Convert README.rst to markdown

Signed-off-by: Aaron Raimist <aaron@raim.ist>

README.rst → README.md

-Olm
-===
+# Olm
 
 An implementation of the Double Ratchet cryptographic ratchet described by
 https://whispersystems.org/docs/specifications/doubleratchet/, written in C and
 C++11 and exposed as a C API.
 
-The specification of the Olm ratchet can be found in `<docs/olm.rst>`_.
+The specification of the Olm ratchet can be found in [docs/olm.md](docs/olm.md).
 
 This library also includes an implementation of the Megolm cryptographic
-ratchet, as specified in `<docs/megolm.rst>`_.
+ratchet, as specified in [docs/megolm.md](docs/megolm.md).
 
-Building
---------
+## Building
 
 To build olm as a shared library run either:
 
-.. code:: bash
-
-    cmake . -Bbuild
-    cmake --build build
+```bash
+cmake . -Bbuild
+cmake --build build
+```
 
 or:
 
-.. code:: bash
-
-    make
+```bash
+make
+```
 
 Using cmake is the preferred method for building the shared library; the
 Makefile may be removed in the future.
 
 To run the tests when using cmake, run:
 
-.. code:: bash
-
-    cd build/tests
-    ctest .
-
+```bash
+cd build/tests
+ctest .
+```
 To run the tests when using make, run:
 
-.. code:: bash
-
-    make test
+```bash
+make test
+```
 
 To build the JavaScript bindings, install emscripten from http://kripken.github.io/emscripten-site/ and then run:
 
-.. code:: bash
-
-    make js
+```bash
+make js
+```
 
 Note that if you run emscripten in a docker container, you need to pass through
 the EMCC_CLOSURE_ARGS environment variable.
 
 To build the android project for Android bindings, run:
 
-.. code:: bash
-
-    cd android
-    ./gradlew clean assembleRelease
+```bash
+cd android
+./gradlew clean assembleRelease
+```
 
 To build the Xcode workspace for Objective-C bindings, run:
 
-.. code:: bash
-
-    cd xcode
-    pod install
-    open OLMKit.xcworkspace
+```bash
+cd xcode
+pod install
+open OLMKit.xcworkspace
+```
 
 To build the Python bindings, first build olm as a shared library as above, and
 then run:
 
-.. code:: bash
-
-    cd python
-    make
+```bash
+cd python
+make
+```
 
 to make both the Python 2 and Python 3 bindings.  To make only one version, use
 ``make olm-python2`` or ``make olm-python3`` instead of just ``make``.
@@ -80,27 +77,25 @@ to make both the Python 2 and Python 3 bindings.  To make only one version, use
 To build olm as a static library (which still needs libstdc++ dynamically) run
 either:
 
-.. code:: bash
-
-    cmake . -Bbuild -DBUILD_SHARED_LIBS=NO
-    cmake --build build
+```bash
+cmake . -Bbuild -DBUILD_SHARED_LIBS=NO
+cmake --build build
+```
 
 or
 
-.. code:: bash
-
-    make static
+```bash
+make static
+```
 
 The library can also be used as a dependency with CMake using:
 
-.. code:: cmake
-
-    find_package(Olm::Olm REQUIRED)
-    target_link_libraries(my_exe Olm::Olm)
-
+```cmake
+find_package(Olm::Olm REQUIRED)
+target_link_libraries(my_exe Olm::Olm)
+```
 
-Release process
----------------
+## Release process
 
 First: bump version numbers in ``common.mk``, ``CMakeLists.txt``,
 ``javascript/package.json``, ``python/olm/__version__.py``, ``OLMKit.podspec``,
@@ -113,34 +108,32 @@ git.
 It's probably sensible to do the above on a release branch (``release-vx.y.z``
 by convention), and merge back to master once the release is complete.
 
-.. code:: bash
+```bash
+make clean
 
-    make clean
+# build and test C library
+make test
 
-    # build and test C library
-    make test
+# build and test JS wrapper
+make js
+(cd javascript && npm run test)
+npm pack javascript
 
-    # build and test JS wrapper
-    make js
-    (cd javascript && npm run test)
-    npm pack javascript
+VERSION=x.y.z
+scp olm-$VERSION.tgz packages@ares.matrix.org:packages/npm/olm/
+git tag $VERSION -s
+git push --tags
 
-    VERSION=x.y.z
-    scp olm-$VERSION.tgz packages@ares.matrix.org:packages/npm/olm/
-    git tag $VERSION -s
-    git push --tags
+# OLMKit CocoaPod release
+# Make sure the version OLMKit.podspec is the same as the git tag
+# (this must be checked before git tagging)
+pod spec lint OLMKit.podspec --use-libraries --allow-warnings
+pod trunk push OLMKit.podspec --use-libraries --allow-warnings
+# Check the pod has been successully published with:
+pod search OLMKit
+```
 
-    # OLMKit CocoaPod release
-    # Make sure the version OLMKit.podspec is the same as the git tag
-    # (this must be checked before git tagging)
-    pod spec lint OLMKit.podspec --use-libraries --allow-warnings
-    pod trunk push OLMKit.podspec --use-libraries --allow-warnings
-    # Check the pod has been successully published with:
-    pod search OLMKit
-
-
-Design
-------
+## Design
 
 Olm is designed to be easy port to different platforms and to be easy
 to write bindings for.
@@ -150,46 +143,40 @@ API. As development has progressed, it has become clear that C++ gives little
 advantage, and new functionality is being added in C, with C++ parts being
 rewritten as the need ariases.
 
-Error Handling
-~~~~~~~~~~~~~~
+### Error Handling
 
 All C functions in the API for olm return ``olm_error()`` on error.
 This makes it easy to check for error conditions within the language bindings.
 
-Random Numbers
-~~~~~~~~~~~~~~
+### Random Numbers
 
 Olm doesn't generate random numbers itself. Instead the caller must
 provide the random data. This makes it easier to port the library to different
 platforms since the caller can use whatever cryptographic random number
 generator their platform provides.
 
-Memory
-~~~~~~
+### Memory
 
 Olm avoids calling malloc or allocating memory on the heap itself.
 Instead the library calculates how much memory will be needed to hold the
 output and the caller supplies a buffer of the appropriate size.
 
-Output Encoding
-~~~~~~~~~~~~~~~
+### Output Encoding
 
 Binary output is encoded as base64 so that languages that prefer unicode
 strings will find it easier to handle the output.
 
-Dependencies
-~~~~~~~~~~~~
+### Dependencies
 
 Olm uses pure C implementations of the cryptographic primitives used by
 the ratchet. While this decreases the performance it makes it much easier
 to compile the library for different architectures.
 
-Contributing
-------------
-Please see `<CONTRIBUTING.rst>`_ when making contributions to the library.
+## Contributing
 
-Security assessment
--------------------
+Please see [CONTRIBUTING.md](CONTRIBUTING.md) when making contributions to the library.
+
+## Security assessment
 
 Olm 1.3.0 was independently assessed by NCC Group's Cryptography Services
 Practive in September 2016 to check for security issues: you can read all
@@ -197,18 +184,16 @@ about it at
 https://www.nccgroup.trust/us/our-research/matrix-olm-cryptographic-review/
 and https://matrix.org/blog/2016/11/21/matrixs-olm-end-to-end-encryption-security-assessment-released-and-implemented-cross-platform-on-riot-at-last/
 
-Bug reports
------------
+## Bug reports
+
 Please file bug reports at https://github.com/matrix-org/olm/issues
 
-What's an olm?
---------------
+## What's an olm?
 
 It's a really cool species of European troglodytic salamander.
 http://www.postojnska-jama.eu/en/come-and-visit-us/vivarium-proteus/
 
-Legal Notice
-------------
+## Legal Notice
 
 The software may be subject to the U.S. export control laws and regulations
 and by downloading the software the user certifies that he/she/it is