title: install multiple versions of protoc on MacOS
body: <p>I'm looking for a way to have multiple versions of protoc available on my Mac (Sierra).</p>
  
  <p>On Windows I have my .exe files on the path whereas the filenames contain the version.</p>
  
  <p>On Mac I found (with brew) versions 2.5, 2.6 and 3.1. If I want to have both 2.5 and 2.6 available how would I achieve that?</p>
  
  <p>Thanks</p>