travis.yml: disabling clang for a while, does not worth the effort

.travis.yml

@@ -1,13 +1,12 @@
-language: cpp
+language:
+  - cpp
 
 compiler:
-  - clang
   - gcc
 
 before_install:
   - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y
   - sudo apt-get update -qq
-  - if [ "$CXX" = "clang++" ]; then sudo apt-get install -qq libstdc++-4.9-dev clang-3.4; fi
   - if [ "$CXX" = "g++" ]; then sudo apt-get install -qq g++-4.9; fi
   - if [ "$CXX" = "g++" ]; then export CXX="g++-4.9" CC="gcc-4.9"; fi