Updated Play tutorial for Play 2.1 and Scala IDE 3.0.0

* I've removed the French translation because I don't really feel like
  maintaining it. That being said, it's easy to bring it back to life.
  (@skyluc, please, don't take offense for this, and feel free to update
  the French tutorial. In the meanwhile, I think it's valuable to have
  the updated English tutorial out asap).

* I have only updated the text, not the images, as this is cumbersome and
  I think having un up-to-date text is sufficient to understand the tutorial.

Fixes #53