title: Specifying a different cache directory for each instance of phantomjs
body: <p>I'm using PhantomJS 1.8 and ran into a limitation -- you can't specify what directory it uses for the disk cache.  I added this to their issue tracking system, but since it wasn't in there before, I wouldn't expect it to be added soon.</p>
  
  <p>So, I'm looking for some way around this limitation.  What I'm trying to do is have multiple Phantomjs processes running, each with their own, separate, cache directory.  Is there a way I can do this until the feature gets added to phantom?  </p>
  
  <p>How does phantom even determine which directory to use for cache in the first place?  If it's based on an environment variable, maybe there could be some way I set a different value for that variable for each instance of PhantomJS that I have running.</p>