Remove finagle-http

Problem

finagle-http is deprecated in favor of finagle-httpx and should be
removed.

See our blog post on upgrading to Netty 4 for more information[1]. Drop
by finaglers[2] if you have any questions.

Solution

Remove finagle-http and convert its dependents to finagle-httpx.

[1] https://finagle.github.io/blog/2014/10/20/upgrading-finagle-to-netty-4/
[2] https://groups.google.com/d/forum/finaglers

RB_ID=746510

doc/src/sphinx/code/BasicServer.scala

@@ -1,5 +1,5 @@
 //#imports
-import com.twitter.finagle.{Http, Service}
+import com.twitter.finagle.{Httpx, Service}
 import com.twitter.io.Charsets
 import com.twitter.server.TwitterServer
 import com.twitter.util.{Await, Future}
@@ -16,7 +16,7 @@ object BasicServer extends TwitterServer {
   }
 
   def main() {
-    val server = Http.serve(":8888", service)
+    val server = Httpx.serve(":8888", service)
     onExit {
       server.close()
     }