add jonathan's examples to the repo
started editing grammar, updating code
Edit tutorial to use fits instead of pyfits

Edit tutorial to consistently use fits instead of pyfits with
appropriate warning about this choice. Keep discussion of extensions
but move to a later paragraph.
Merge pull request #3 from jfoster17/fits-header

Fits header
Merge pull request #1 from adrn/fits-header

Add jonathan's examples to the repo