Remove ResponseBuilder.

Closes #98.
Merge branch 'master' into topic/remove-response-builder

Conflicts:
	servlet/src/main/scala/org/http4s/servlet/Http4sServlet.scala
Finish the job of removing the ResponseBuilder.
Merge branch 'master' into topic/remove-response-builder

Conflicts:
	blaze-server/src/test/scala/org/http4s/server/blaze/ServerTestRoutes.scala
	core/src/test/scala/org/http4s/EntityDecoderSpec.scala
	jawn/src/test/scala/org/http4s/jawn/JawnDecodeSupportSpec.scala
Merge pull request #142 from http4s/topic/remove-response-builder

Remove ResponseBuilder.