title: Github - Cleaning up branches after they're merged as part of a pull request
body: <p>I'm working on improving team processes around merging and consolidating changes and would like to use Pull Requests in GitHub as a way to better manage changes.</p>
  
  <p>My one concern about this is that I want to ensure that after merging a pull request, that the branch that has been merged is removed (I want the commits to stay, but I don't want our repository to be filled with a lot of stale branches that are no longer needed).</p>
  
  <p>What's the best / safest way to accomplish this (preferably with the minimum number of steps, because with more steps there's more chance of one being forgotten).</p>