Cross-platform compatibliity

[scivision]

Fortran is designed to compile anywhere; these minimal changes help ensure anyone can quickly compile and use Glow regardless of PC/operating system by:

1. swap platform-specific commands with equivalent platform-agnostic commands.
2. enable continuous integration (build/run self-test on every git push or pull request)
3. separately, enabling the Python easy-access interface that also enables Matlab direct access to Glow subroutines and functions
4. Optional CMake makes cross-platform builds easier, and includes optional MPI.

Re 2) & 3): checkout https://travis-ci.org/scivision/GLOW to see the build status, which automatically runs on a virtual machine for Mac OS X and Linux whenever a change is made by anyone to the code. One would add more detailed registration cases. Windows can also be added.