Initial commit of admin-workflow

- describes workflow of admins after receiving a developer pull request
- addresses [Pivotal Tracker issue 76274824](https://www.pivotaltracker.com/story/show/76274824)
- almost the same as file previously pushed, then deleted, except that it is in its own branch so it can be merged separately from developer-workflow
- now includes:
  - examples show SSH (instead of HTTPS)