Preparing release 3.1.2

git-svn-id: http://svn6.assembla.com/svn/pyfits/branches/3.1-stable@2163 ed100bfc-0583-0410-97f2-c26b58777a21
Back to development: 3.1.3

git-svn-id: http://svn6.assembla.com/svn/pyfits/branches/3.1-stable@2164 ed100bfc-0583-0410-97f2-c26b58777a21