Update for Scala 2.10 and associated deps, also fixes a Salat issue of a missing custom context for Play Classloader.

Hello,

Please consider merging these changes in to provide:
1) Update to:
 - Scala 2.10.0
 - Casbah 2.5-SNAPSHOT
 - Salat 1.9.2-SNAPSHOT

2) Addition of a custom context that adds Play's class loader to fix:

Caused by: com.novus.salat.util.GraterGlitch: 

      GRATER GLITCH - unable to find or instantiate a grater using supplied path name

      REASON: Very strange!  Path='models.Registration' from pickled ScalaSig causes ClassNotFoundException

      Context: 'global'
      Path from pickled Scala sig: 'models.Registration'