distance > 0
now with optional kwarg allow_negative
added test of new kwarg
added note in coordinates docs about negative distances
update error message
added line about distance change to changelog
Add CHANGES section for 0.3.2
Make `@deprecated` decorator work for classes.
Fix pickling issues with class deprecation.  Fix Python 2.6 bug.
Standardize how Python version checking is done.
Add changes to io.fits
 Fix #2173: axis keyword in median_absolute_deviation.

The axis keyword in median_absolute_deviation is now taken into
account for any axis, and the data properly broadcasted.  The
corresponding unit test is updated.
Added Wien wavelength displacement law constant.
Fixing all but auto-generated links in coordinates
Fixing issues for PR 2192
Due to docstest failures changing back line wraps to 80+ characters
Minor modification of error messages