PIL vs imagemagick

[Will Kahn-Greene]

We're having some issues with getting PIL installed into the
development environment. Chris talked with the deviantart folks and
discovered they're not using PIL--they're using imagemagick.

This issue is for the following:


1. researching the pros/cons of switching
2. checking to see if there are other options
3. if it seems like a good idea and the other options aren't
   enticing, looking at switching GNU MediaGoblin over to using
   imagemagick
4. if 3 happens, then updating all the docs