Use GCC5 on travis for linux
Use GCC5 on travis for linux

BFH-E1D-2015-2016/SuperTeacher,LarsAeschlimann/SuperTeacher,NicoHaui/SuperTeacher,LarsAeschlimann/SuperTeacher,NicoHaui/SuperTeacher,NicoHaui/SuperTeacher,BFH-E1D-2015-2016/SuperTeacher