Kill megasky

Replaces megasky with an internal megaplot call to make sky maps.

No longer produces a fits file, instead makes a 2-d histogram of the sky posterior, and plots on a Mollweide projection. If it's an injection done from an xml file, the injected location is also plotted. An example output page with the new sky map is here.

bayeswave_pipe is updated to no longer make megasky jobs. megasky.py still lives in the repository (with a warning) for the limited number of power users who may need to actually make fits files.