Merge pull request #5 from torbjoernk/feature/mpi-pf

cmake: some more output on compiler selection
travis: Echo more compiler info.
cmake: try find system-wide FFTW3 before self-compiling it

The policy is to first try to find a system installation of FFTW3 (i.e.
searching for a fftw3.h and libfftw3.so). Iff this fails, CMake will
download and compile a static library of FFTW3 on its own in the build
directory of PFASST++.

this should fix #54
travis: make travis use Ubuntu's libfftw3
Merge pull request #55 from torbjoernk/feature/cmake-fftw

Let CMake find and use preinstalled FFTW3
Merge remote-tracking branch 'upstream/development' into feature/mpi-pf

Conflicts:
	.travis.yml
Merge branch 'feature/mpi-pf' of github.com:memmett/PFASST into feature/mpi-pf
cmake: Change how we're handling MPI.
travis: Tidy and add full path for MPI example.
cmake: use MPI compiler again if applicable