Preparing release 3.1.6

Conflicts:

	CHANGES.txt
	docs/source/conf.py
	setup.cfg

git-svn-id: http://svn6.assembla.com/svn/pyfits/trunk@2731 ed100bfc-0583-0410-97f2-c26b58777a21
Updating v3.2.3 release date

git-svn-id: http://svn6.assembla.com/svn/pyfits/trunk@2732 ed100bfc-0583-0410-97f2-c26b58777a21