Release note review

Review edits for https://github.com/python-pillow/Pillow/pull/1032

 * English changes.
 * Renamed filename to 2.7.0 because we may have a 2.7.1.
 * Similarly, refer to 2.7.0 in the document rather than 2.7, and "Pillow 2.7.0" just so there's no confusion with Python 2.7.x.


Again, both are fine. But we know for sure it was in the previous version and some previous versions, but of course not all (for example those before it was even implemented).