Add exdoc.

Author: Samuel Seay

mix.exs

@@ -22,6 +22,7 @@ defmodule PageObject.Mixfile do
     [{:hound, "~> 1.0.1"},
      {:cowboy, "~> 1.0.3", only: :test},
      {:plug, "~> 1.0", only: :test},
+     {:ex_doc, ">= 0.0.0", only: :dev},
      {:inflex, "~> 1.7.0" }]
   end