Merge pull request #2181 from eteq/status-to-jac

Fix/clarify covariance matrix in NonLinearLSQFitter
This implements a change @wkerzendorf and I had tossed around some time
back of eliminating the need to provide a parameter's name twice when
defining the Parameter attributes on a Model subclass.

In other words, rather than having to write
``amplitude = Parameter('amplitude')`` one should be able to write just
``ampltiude = Parameter()`` and have the name automatically taken from
the class attribute (in fact, it is required that they be the same or
else other parts of the code will break--this requirement has now been
made explicit with a check in _ModelMeta.__new__).

This might be considered very "magic", but it's not the only aspect of
Parameter that's magical to begin with.  It also makes the code I think
terser and easier to read.
Fix overflow test to work on numpy 1.5
Add known issue that overflowing ints get cast to float in ascii.read for numpy 1.5
Merge pull request #2107 from mdboom/wcs/wcslib-4.21

astropy.wcs failing to recognize invalid region in ZPN and HPX projections
Add docs for setting data_start to 'guess'
Updated CHANGES.rst
Add changelog entry
Merge pull request #1712 from mwcraig/developer-docs

Reorganization of developer documentation
Merge pull request #2221 from larrybradley/patch-1

Update docguide.rst
Added change log for #2129
Merge pull request #2129 from RayPlante/vo-format-fix

vos_catalog.py: fix use of format() for compat with python 2.6
Merge pull request #2243 from pllim/changelog-for-2129

Added change log for Astropy Issue 2129
Add comment line in test referencing issue numbers
Merge pull request #2234 from taldcroft/catch-overflow

In io.ascii, fall back to string if integers are too large
Support numpy 1.5.x by making one of the tests accept TypeError or ValueError
Changelog entry was added to wrong section in 9c5debf
Update codeguide.rst

Fix typo.
Fix #2230: Make the progressbar work with the IPython qtconsole.
Add CHANGES entry.