Bump us to sbt 0.13.1.
Liftsh is now smart enough to download the sbt launcher for you.
Ignore the sbt launcher jar under project/
Merge remote-tracking branch 'origin/master' into zero-point-thirteen

Conflicts:
	build.sbt
Start pulling the yui compressor plugin from git directly.
Somehow 2.10.0 ended up as the default version? Fixed.
Bump sbt to version 0.13.5.
Merge pull request #1537 from lift/zero-point-thirteen

Bump to sbt 0.13.5.