Newer cmake for Travis Linux worker

cmake/travis_before_install_linux.sh

@@ -2,5 +2,6 @@
 
 sudo add-apt-repository -y ppa:zoogie/sdl2-snapshots
 sudo add-apt-repository -y ppa:ubuntu-toolchain-r/test
+sudo add-apt-repository -y ppa:kalakris/cmake
 sudo apt-get -qq -y update