Fix travis

.travis.yml

@@ -7,7 +7,7 @@ sudo: true
 
 before_install:
 # Qt >= 5.2
- - sudo add-apt-repository -y ppa:beineri/opt-qt541
+ - sudo add-apt-repository -y ppa:beineri/opt-qt542
 # GCC >=4.8
  - if [ "$CXX" == "g++" ]; then sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test; fi
  - if [ "$CXX" == "clang++" ]; then sudo add-apt-repository -y ppa:h-rayflood/llvm; fi