Swapping cosmics for cosmicx

Removes `cosmics.py` from the pipeline. Cosmic ray rejection is instead accomplished, significantly more quickly, by the python-wrapped c program `lacosmicx`, by C. Mccully. `setup.py` now builds the c code in addition to installing the python package. `README.md` was edited to reflect this change.

 A new wrapper around `lacosmicx`, 'run_cosmicx.py', is added. It largely mirrors the structure of the previous `run_cosmics.py`. A significant difference between the two is the use of `astropy.io' in place of 'pyfits', which results in a sight increase in speed.

The five second delay in `cgi_session()` in `jpl2db` has also been removed, reducing retrieval from JPL's Horizons ephemeris to about 0.7 seconds.