Update earmark and ex_doc

mix.exs

@@ -8,7 +8,7 @@ defmodule Httparrot.Mixfile do
   def project do
     [
       app: :httparrot,
-      version: "1.2.0",
+      version: "1.3.0",
       elixir: "~> 1.7",
       name: "HTTParrot",
       description: @description,
@@ -29,7 +29,8 @@ defmodule Httparrot.Mixfile do
       {:cowboy, "~> 2.8.0"},
       {:exjsx, "~> 3.0 or ~> 4.0"},
       {:con_cache, "~> 0.14.0"},
-      {:ex_doc, "~> 0.14", only: :dev},
+      {:earmark, "~> 1.0", only: :dev},
+      {:ex_doc, "~> 0.18", only: :dev},
       {:meck, "~> 0.8.13", only: :test}
     ]
   end