Restructured .travis.yml

.travis.yml

@@ -5,15 +5,15 @@ dist: trusty
 
 matrix:
   include:
-    - compiler: gcc
+    - os: linux
-      install:
+      compiler: gcc
-        - sudo apt-get -y install g++-5
+      before_install:
-      env: COMPILER=g++-5
-before_install:
         - sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
         - sudo apt-get -q update
+      install:
+        - sudo apt-get -y install g++-5
         - sudo apt-get -y install libboost-all-dev
-script:
+      script:
         - mkdir build
         - cd build
-  - cmake -DCMAKE_CXX_COMPILER=$COMPILER .. && make
+        - cmake -DCMAKE_CXX_COMPILER=g++-5 .. && make