Clean up stale branches (23 fully merged)

There are currently 35 branches in the repo. 23 of them have no unmerged commits. I've compiled a list of branches that I believe are safe to delete.

Fully merged Branches to delete (0 commits ahead, only behind master).
- add-crontab (last commit: Jan 28)
- add-some-fault-tolerance (last commit: 2014)
- beechnut-develop (last commit: 2014)
- better_dev (Mar 18)
- cleanup/remove-legacy-ruby-code (Apr 8)
- cleanup-and-merge-for-demo (Feb 10)
- dev-setup (Mar 11)
- feature/update-main-posters (Feb 25)
- fix/instagram-post (Apr 8)
- fix/rescuegroups-api (Mar 11)
- fix-tests (Apr 1)
- hashtags (2014)
- heroku-button (2014)
- instagram-integration (Feb 10)
- interfaces2 (Feb 18)
- j2_interfaces (Feb 4)
- j2_test (Jan 28)
- logo (2014)
- mw/test-workflow (Jan 21)
- pet-adoption-url (Apr 1)
- post_with_url (Apr 1)
- prajwal-local (Mar 11)
- upgrade-instagram-poster (Apr 1)

Orphaned (has zero shared git history with master)

- cfa-heroku-button (2014, no common ancestor with master)