Fix dead link to the stpyfits 'documentation' (what little there is)

git-svn-id: http://svn6.assembla.com/svn/pyfits/trunk@2168 ed100bfc-0583-0410-97f2-c26b58777a21
Removed all assert_ functions except for assert_raises; renamed all 'pyfits' imports to just 'fits'.  This will make merges between Astropy significantly less troublesome in most cases.

git-svn-id: http://svn6.assembla.com/svn/pyfits/trunk@2169 ed100bfc-0583-0410-97f2-c26b58777a21
Replaced references to ticket numbers with the full ticket URL so as to elimitate ambiguity between GitHub issues and tickets from Trac.

git-svn-id: http://svn6.assembla.com/svn/pyfits/trunk@2170 ed100bfc-0583-0410-97f2-c26b58777a21