Update gitignore because of oslo setup.py

Change I6ed3a97e35ce73b820f7a436214480051ed6528f started using
setup.py in oslo. This adds support for auto generating the AUTHORS
and ChangeLog files.

This adds these files to gitignore and adds a .mailmap to cleanup the file.

Fixes bug 979958.

Change-Id: If61920c81499c5e579d3c1e7a66f8bf02020dfa9
Merge "Update gitignore because of oslo setup.py"