0.56:
	implement anwcs_write_to
	Makefile files for install-indexes
	add -std=gnu89 to default CFLAGS
	add clip_wcs() method

0.55:
	Fix bug in WCS numpy array iterators

0.54:
	Try importing pyfits and then astropy.io.fits

0.53:
	Update wcs-pv2sip and include in default build
	Fixes for git version strings
	Read and write linear SIP distortion terms
	multiindex: don't assert when reloading already-loaded file

0.52:
	Fix release version strings in released versions.

0.51:
	Fix half-pixel bug in "solve-field --crpix-center": the center was
	set to 1 + {W,H}/2, not 0.5 + {W,H}/2.  (The WCS was still
	correct, the CRPIX was set to a half pixel in each dimension away
	from the center pixel.


