Try to get gcc-5 (please travis, just work!)

.travis.yml

@@ -9,10 +9,10 @@ addons:
         sources:
         - ubuntu-toolchain-r-test
         packages:
-        - gcc-4.8
-        - g++-4.8
+        - gcc-5
+        - g++-5
         - cmake
 
 sudo: false
 install:
-    - if [ "$CXX" = "g++" ]; then export CXX="g++-4.8" CC="gcc-4.8"; fi
+    - if [ "$CXX" = "g++" ]; then export CXX="g++-5" CC="gcc-5"; fi