Add Gentoo build and installation instructions (#45)

README.md

@@ -15,7 +15,13 @@ but you can of course receive and send messages in the rooms that you are a memb
 
 #### Arch Linux
 ```bash
-pacaur -S nheko-git
+$ pacaur -S nheko-git
+```
+
+#### Gentoo Linux
+```bash
+$ sudo layman -a matrix
+$ sudo emerge -a nheko
 ```
 
 #### Windows
@@ -37,6 +43,12 @@ You can find a NSIS installer [here](https://ci.appveyor.com/project/mujx/nheko/
 $ sudo pacman -S qt5-base qt5-tools cmake gcc fontconfig
 ```
 
+##### Gentoo Linux
+
+```bash
+$ sudo emerge -a ">=dev-qt/qtgui-5.7.1"	media-libs/fontconfig
+```
+
 ##### Ubuntu 14.04
 
 ```bash

dist/Gentoo/Manifest

+EBUILD nheko-9999.ebuild 790 SHA256 d1b8032bbe7d93efb48dac4dc34dbdb5d194a6435c448e3a2591dbcb7f1b9de4 SHA512 27a69788584beaccbb9ff80e229fe80f8f955b16aa6b25271e2ad099c9d18c81f8e2edd06b377dab440494b22814383a080e2c1a0983ad52b376810327a4364c WHIRLPOOL 4fae4e2a628032d3b149ae0778145c20ff1ca4d1d0fa63bb36e0a13ad0f0bea4704500ac5467fe7f311565d347c179862f5b783475cecb4523854506bf2f3421

dist/Gentoo/nheko-9999.ebuild

+# Copyright 1999-2017 Gentoo Foundation
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=6
+
+DESCRIPTION="Desktop client for the Matrix protocol"
+HOMEPAGE="https://github.com/mujx/nheko"
+
+inherit git-r3 eutils cmake-utils
+
+if [[ ${PV} == "9999" ]]; then
+	SRC_URI=""
+	EGIT_REPO_URI="git://github.com/mujx/nheko.git"
+fi
+
+LICENSE="GPL-3"
+SLOT="0"
+IUSE=""
+
+DEPEND=">=dev-qt/qtgui-5.7.1
+		media-libs/fontconfig"
+RDEPEND="${DEPEND}"
+
+src_configure() {
+	cmake-utils_src_configure
+}
+
+src_compile() {
+	emake DESTDIR="${D}"
+}
+
+src_install() {
+	local icon_size
+    for icon_size in 16 32 48 64 128 256 512; do
+        newicon -s "${icon_size}" \
+			"${S}/resources/nheko-${icon_size}.png" \
+			nheko.png
+    done
+
+	domenu ${S}/resources/nheko.desktop
+
+	dobin ${S}/build/nheko
+}