posting-comment-on-integration

### Changelog
* re-organization of github methods
moved github authorization methods to their own module

* added comment posting to pr when integrating
added ability for git integrate to post a comment to the pull request
for that branch
https://trello.com/c/fferpTi8/304-automate-posting-comment-on-pull-reque
st-when-integrating-into-staging
add unit test for when pull request does not exist and decide whether to:
1. skip comment creation
2. auto-create pull request