Add another release step [ci skip]

Author: asottile

CONTRIBUTING.rst

@@ -60,6 +60,7 @@ Here's a brief check list for releasing a new version:
   It's currently a static website deployed on GitHub Pages.
   Use ``python setup.py upload_doc`` command.
   Although it seems possible to be automated using Travis.
+- Manually create a release through https://github.com/dahlia/libsass-python/releases/
 
 Ping Hong Minhee (hongminhee@member.fsf.org, @dahlia on GitHub) if you need
 any help!