Fix #492.  Raise an exception when an invalid type is passed to the Unit constructor.
Merge branch 'fits/astropy' into astropy

This merges up through r1927 from pyfits' trunk in SVN.  Closes the following
issues in Astropy:

Closes #339 astropy.io.fits.Header totextfile and Header.__init__ disagree on 'endcard' convention
Closes #318 Move io.fits external C dependencies into cextern

Conflicts:
	README.txt
	astropy/io/fits/src/compress.c
	astropy/io/fits/src/crc32.h
	astropy/io/fits/src/deflate.h
	astropy/io/fits/src/fits_hcompress.c
	astropy/io/fits/src/fits_hdecompress.c
	astropy/io/fits/src/fitsio.c
	astropy/io/fits/src/fitsio.h
	astropy/io/fits/src/inffast.c
	astropy/io/fits/src/inffast.h
	astropy/io/fits/src/inffixed.h
	astropy/io/fits/src/inflate.h
	astropy/io/fits/src/inftrees.c
	astropy/io/fits/src/inftrees.h
	astropy/io/fits/src/pliocomp.c
	astropy/io/fits/src/quantize.c
	astropy/io/fits/src/ricecomp.c
	astropy/io/fits/src/ricecomp.h
	astropy/io/fits/src/trees.c
	astropy/io/fits/src/trees.h
	astropy/io/fits/src/zlib.c
	astropy/io/fits/src/zlib.h
	astropy/io/fits/src/zutil.h
	cextern/cfitsio/crc32.h
	cextern/cfitsio/deflate.h
	cextern/cfitsio/fits_hcompress.c
	cextern/cfitsio/fits_hdecompress.c
	cextern/cfitsio/inffast.c
	cextern/cfitsio/inffixed.h
	cextern/cfitsio/inftrees.c
	cextern/cfitsio/pliocomp.c
	cextern/cfitsio/quantize.c
	cextern/cfitsio/ricecomp.c
	cextern/cfitsio/trees.c
	cextern/cfitsio/trees.h
	cextern/cfitsio/zutil.h
	setup.cfg
	src/crc32.h
	src/deflate.h
	src/fits_hcompress.c
	src/fits_hdecompress.c
	src/inffast.c
	src/inffixed.h
	src/inftrees.c
	src/pliocomp.c
	src/quantize.c
	src/ricecomp.c
	src/trees.c
	src/trees.h
	src/zutil.h
	tox.ini

Conflicts:

	astropy/io/fits/diff.py
	astropy/io/fits/hdu/base.py
	astropy/io/fits/hdu/compressed.py
	astropy/io/fits/hdu/image.py
	astropy/io/fits/src/compressionmodule.c
	astropy/io/fits/tests/cfitsio_verify.c
	astropy/io/fits/tests/test_core.py
	astropy/io/fits/tests/test_header.py
	astropy/io/fits/tests/test_image.py
	astropy/io/fits/tests/test_uint.py
Fixed up the astropy.fits.io package setup to support linking the compression module with a system version of CFITSIO.
This little _is_mmap hack is unnecessary in Astropy since we don't support Python 2.5.
Added all the bug fixes from the last pyfits merge to the astropy changelog.  At this point the pyfits changes kind of dominate the changelog. I hope that's okay but if not we could think of a way of collapsing it (though I'd rather not; the 'What's New' page in the docs will provide a broader overview, I think.
Merge branch 'pyfits/astropy' into astropy

This *should* fix all the issues that were causing the build to fail in

Conflicts:

	astropy/io/fits/util.py
Merge branch 'pyfits/astropy' into astropy

Conflicts:
	README.txt

Conflicts:

	astropy/io/fits/src/compressionmodule.c
Merge branch 'master' into astropy
Add the compressionmodule header.
Fix missing import
Ignore generated .pyd files.
Add some compiler flags needed to compile cfitsio in MSVC.
updated exception messages on Time initializer to be a bit more clear/explicit
added support for passing a Time object into Time initializer
added test to ensure initializer copying works
Use __new__ and replicate() to allow init with Time/TimeDelta object
Add more tests of init with Time/TimeDelta object
Merge pull request #6 from taldcroft/time-init-additions

Modified approach for time init additions
Upgrade to wcslib-4.16
Ignore astropy/extern directory for testing.  We don't have tests in there anyway, and this prevents the external code from being included in the PEP8 compliance report.  (I tried pep8ignore, but couldn't get that to work).