title: Github Merge Changes to Master before or after Pull Request
body: <p>I've checked out a branch for a <code>pandas</code> issue, made changes and commited. </p>
  
  <p>Should I merge my branch into the master branch of my fork of pandas and make a pull request of that, or should I make a pull request from the new branch and let  someone with write privileges merge that branch <code>into pandas-dev/master</code>?</p>