Cleanup fortran files

[jklenzing]

Replace msis file with official release from https://map.nrl.navy.mil as base. Modifications added to independently scale Tinf, as well as make compatible with gfortran.

Removed unused files from hwm.

This still needs a comparison to see if physical output is realistic.

[jklenzing]

Updated setup file with new python versions

[jklenzing]

Updated travis to xenial for all versions to be more future-compatible.

[jklenzing]

Added official version of hwm and general cleanup.

Verified that code runs and generates reasonable output.

Ready for review.

[JonathonMSmith]

perhaps in the README.md there should be a statement about setting the paths using utils. This looks good though and I think it's ready for a push. If you'd like to make those changes to the filenames I'll look forward to reviewing that.

[jklenzing]

New file uploaded. Had to update the line endings to get diff to run. Mostly changes to comments, but I caught a few new lines of code as well.

I'll update the documentation as part of the documentation branch I'm working on.

[jklenzing]

perhaps in the README.md there should be a statement about setting the paths using utils.

Added this to #57 as part of planned update to user directory.