Upgrade play-iteratee.
Replace enumerators with iteratee callbacks.
Simplify types.
Eliminate handler.
Make stringHandler more useful for routes that return futures.
Parameterize body types.
Revert to Enumerator bodies. Simpler, but I'm still queasy about this.
Reinstate servlet example.
Merge branch 'develop' into netty

Conflicts:
	core/src/main/scala/org/http4s/MockServer.scala
	core/src/main/scala/org/http4s/Request.scala
	core/src/main/scala/org/http4s/package.scala