move all the model subpackages into one doc section on models
Added valid-package-names option to automodapi
Added initial CONTRIBUTING.md file
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
Merge pull request #1871 from eteq/astropy-deprecation-show

Make `AstropyDeprecationWarning`s appear by default in py2.7
Merge branch 'models-onesection' into staging