Add AUTHORS and ChangeLog to .gitignore
Add AUTHORS and ChangeLog to .gitignore

pbr generates these.

Change-Id: I0d1a43184b6dcf4f725bb57ee6ba09ce6f3cae2a

gilbertpilz/solum,gilbertpilz/solum,openstack/solum,gilbertpilz/solum,devdattakulkarni/test-solum,stackforge/solum,stackforge/solum,openstack/solum,ed-/solum,mohitsethi/solum,ed-/solum,gilbertpilz/solum,devdattakulkarni/test-solum,julienvey/solum,ed-/solum,mohitsethi/solum,julienvey/solum,ed-/solum