Added checking for fixed-format mandatory keywords in __init__ and fromstring methods.  For your reference, the mandatory keywords are: SIMPLE, BITPIX, NAXIS, NAXISn, XTENSION, PCOUNT, GCOUNT, EXTEND, and END.
Added checking for fixed-format mandatory keywords in __init__ and fromstring
methods.  For your reference, the mandatory keywords are: SIMPLE, BITPIX,
NAXIS, NAXISn, XTENSION, PCOUNT, GCOUNT, EXTEND, and END.


git-svn-id: 5305e2c1a78737cf7dd5f8f44e9bbbd00348fde7@25 ed100bfc-0583-0410-97f2-c26b58777a21

embray/PyFITS,embray/PyFITS,spacetelescope/PyFITS,spacetelescope/PyFITS,embray/PyFITS,embray/PyFITS