Added initial CONTRIBUTING.md file
Merge pull request #1867 from mdboom/table/sort

Table sort fails for unicode fields in numpy 1.5
Remove DeprecationWarning superclass for AstropyDeprecationWarning

we do this because in py2.7, DeprecationWarning and subclasses are hidden by default, but we want astropy's deprecations to get shown by default
Implemented comments by @eteq
Modified section title as suggested by @taldcroft
Merge pull request #1866 from astrofrog/add-contributing

Create CONTRIBUTING file
Remove some orphaned code in Table.groups
Fix import failure on Python 3 if setup.py exists in current dir
Make import work from within build directory by checking for setup.py
Merge pull request #1874 from taldcroft/table/orphaned-code

Remove some orphaned code in Table.groups
Minor cleanup of CHANGES.rst formatting, add issue 1809
Add issue number for doctests change
Merge pull request #1863 from taldcroft/docs/changes-cleanup

Minor cleanup of CHANGES.rst formatting, add issue numbers
Merge pull request #1877 from taldcroft/init-setup

Import fails on Python 3 if setup.py exists in current directory
Add PR number to CHANGES.rst
Add PR number to CHANGES.rst
Add no-heading option to the automodapi sphinx ext

This add the option to not have the auotmodapi extension add a top
level title, i.e `astropy.nddata Module`.
couple of docstring typos
Bugfix entry to CHANGES.rst
Rewrite use of _validate_angles in __setitem__ following @taldcroft's comment