Travis CI: Use Ubuntu 14.04 instead of 12.04 and GCC 6 instead of 4
Travis CI: Use Ubuntu 14.04 instead of 12.04 and GCC 6 instead of 4

Use a much newer Ubuntu version and use a much newer GCC.

usev6/rakudo,sjn/rakudo,sjn/rakudo,salortiz/rakudo,nbrown/rakudo,rakudo/rakudo,usev6/rakudo,labster/rakudo,softmoth/rakudo,raydiak/rakudo,jonathanstowe/rakudo,MasterDuke17/rakudo,raydiak/rakudo,salortiz/rakudo,tony-o/rakudo,labster/rakudo,usev6/rakudo,nbrown/rakudo,usev6/rakudo,rakudo/rakudo,awwaiid/rakudo,sjn/rakudo,softmoth/rakudo,tony-o/rakudo,softmoth/rakudo,labster/rakudo,tbrowder/rakudo,salortiz/rakudo,MasterDuke17/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,tbrowder/rakudo,samcv/rakudo,awwaiid/rakudo,tbrowder/rakudo,softmoth/rakudo,salortiz/rakudo,salortiz/rakudo,MasterDuke17/rakudo,jonathanstowe/rakudo,nbrown/rakudo,tony-o/rakudo,labster/rakudo,Gnouc/rakudo,lucasbuchala/rakudo,labster/rakudo,samcv/rakudo,Gnouc/rakudo,jonathanstowe/rakudo,MasterDuke17/rakudo,labster/rakudo,rakudo/rakudo,nbrown/rakudo,jonathanstowe/rakudo,sjn/rakudo,tony-o/rakudo,samcv/rakudo,Gnouc/rakudo,awwaiid/rakudo,tony-o/rakudo,rakudo/rakudo,awwaiid/rakudo,nbrown/rakudo,Gnouc/rakudo,lucasbuchala/rakudo,samcv/rakudo,Gnouc/rakudo,sjn/rakudo,tbrowder/rakudo,salortiz/rakudo,raydiak/rakudo,rakudo/rakudo,samcv/rakudo,lucasbuchala/rakudo,tbrowder/rakudo,usev6/rakudo,lucasbuchala/rakudo,Gnouc/rakudo,rakudo/rakudo,MasterDuke17/rakudo,raydiak/rakudo,jonathanstowe/rakudo,tony-o/rakudo,nbrown/rakudo,awwaiid/rakudo,softmoth/rakudo,lucasbuchala/rakudo