Make pyfits an optional dependancy with astropy.io.fits first
Build deps and setup.py changed from pyfits to astropy
Merge remote-tracking branch 'upstream/staging' into pyfits

Conflicts:
	.travis.yml
	setup.py
Fix fails due to pyfits.core
Merge pull request #488 from Cadair/pyfits

Deprecate pyfits in place of astropy