Try to fix c++11 support in .travis.yml

.travis.yml

@@ -1,7 +1,13 @@
 language: cpp
-compiler: clang
+compiler:
+  - clang
+  - gcc
 before_install:
+  - sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y 
   - sudo apt-get update -qq
+  - if [ "$CXX" = "clang++" ]; then sudo apt-get install -y libstdc++-4.8-dev; fi
+  - if [ "$CXX" = "g++" ]; then sudo apt-get install -y g++-4.8; fi
+  - if [ "$CXX" = "g++" ]; then export CXX=g++-4.8; fi
   - sudo apt-get install -y libncursesw5-dev
   - sudo apt-get install -y libboost-regex-dev
 script: cd src && make && make test