Fixed Travis CI license header check.
Fixed Travis CI license header check.

The license header has not been checked for CMake files, yet.

RWTH-ELP/PnMPI,RWTH-HPC/PnMPI,RWTH-ELP/PnMPI,RWTH-ELP/PnMPI,RWTH-HPC/PnMPI,RWTH-HPC/PnMPI