Travis CI support

Hey Felix,

I addad a `.travis.yml` file to check commits and pull-requests with
  https://travis-ci.org/ComputationalRadiationPhysics/libSplash

### Further features in this pull request

- ( *Bugfix* ) MPI_Finalize problem for tests
- ( *Disabled* ) Parallel_SimpleDataTest does not compile ( *fix-me* )
- ( *Disabled* ) No support for `master` and `axel` branch for now
- ( *Feature* ) tests/run* scripts return an accumulated error number now

Cheers! :8ball: