Merge pull request #17 from eteubert/master

This fixes an error when building under Mix 1.9.0. See:
* a5fb55b#commitcomment-20730235
* elixir-lang/elixir#9163 (comment) 

Closes #12, #14, #15, #16.

mix.exs

@@ -12,8 +12,7 @@ defmodule RemoteIp.Mixfile do
   end
 
   def application do
-    [applications: [:plug],
-     included_applications: [:combine, :inet_cidr]]
+    [applications: [:plug, :combine, :inet_cidr]]
   end
 
   defp description do