generic enumeratee writable

Can make a writable for a Enumeratee[HttpChunk,A] with available
SimpleWritable[A]
Netty version bump: 4.0.10
Replace scopes with an immutable attribute map.
Move to top level to reduce import tax.
Merge branch 'develop' into topic/scalaz-task

Conflicts:
	core/src/main/scala/org/http4s/Responder.scala
	core/src/main/scala/org/http4s/attributes/scopes.scala
	core/src/main/scala/org/http4s/model.scala
	core/src/main/scala/org/http4s/package.scala
	core/src/test/scala/org/http4s/ExampleRoute.scala
	core/src/test/scala/org/http4s/attributes/ScopeSpec.scala
	examples/src/main/scala/org/http4s/examples/ExampleRoute.scala