Use Qt 5.9.2 on travis

.ci/install.sh

@@ -13,7 +13,7 @@ fi
 if [ $TRAVIS_OS_NAME == linux ]; then
 
     if [ -z "$QT_VERSION" ]; then
-        QT_VERSION="594"
+        QT_VERSION="592"
     fi
 
     export QT_PKG=${QT_VERSION:0:2}

.travis.yml

@@ -22,7 +22,7 @@ matrix:
           env:
               - CXX_COMPILER=g++-6
               - C_COMPILER=gcc-6
-              - QT_VERSION=594
+              - QT_VERSION=592
               - DEPLOYMENT=1
           addons:
               apt:
@@ -43,7 +43,7 @@ matrix:
           env:
               - CXX_COMPILER=clang++-5.0
               - C_COMPILER=clang-5.0
-              - QT_VERSION=594
+              - QT_VERSION=592
           addons:
               apt:
                   sources: ["ubuntu-toolchain-r-test", "llvm-toolchain-trusty-5.0"]