Travis: OpenMPI 1.5.1+ and HDF5 1.8.6+

- OpenMPI >= 1.5.1 (atm 1.5.4)
- HDF5 >= 1.8.6 (atm 1.8.11)
- thx to the "donator PPAs" of Jose Sabater (@jsm-8, hdf5 1.8.11) and James Page (@james-page, OpenMPI dependency)