Responder => Response, Charset => CharacterSet

Eliminates some conflicts with standard library, and brings us closer
to the scalaz-task branch, which will reduce merge headaches during
our ongoing indecision.
Merge branch 'develop' into topic/scalaz-task

Conflicts:
	core/src/main/scala/org/http4s/BodyParser.scala
	core/src/main/scala/org/http4s/Chunk.scala
	core/src/main/scala/org/http4s/MockServer.scala
	core/src/main/scala/org/http4s/PushSupport.scala
	core/src/main/scala/org/http4s/Response.scala
	core/src/main/scala/org/http4s/Writable.scala
	core/src/main/scala/org/http4s/package.scala
	core/src/main/scala/org/http4s/util/middleware/URITranslation.scala
	grizzly/src/main/scala/org/http4s/grizzly/Http4sGrizzly.scala
	netty/src/main/scala/org/http4s/netty/Http4sNetty.scala
	servlet/src/main/scala/org/http4s/servlet/Http4sServlet.scala