Upgrade to ex_doc 0.12.0

mix.exs

@@ -38,7 +38,7 @@ defmodule Thrift.Mixfile do
   end
 
   defp deps do
-     [{:ex_doc, "~> 0.11.4", only: :dev},
+     [{:ex_doc, "~> 0.12.0", only: :dev},
       {:earmark, "~> 0.2.1", only: :dev},
       {:excoveralls, "~> 0.5.4", only: :test},
       {:dialyze, "~> 0.2.0", only: [:dev, :test]}

mix.lock

@@ -1,7 +1,7 @@
 %{"certifi": {:hex, :certifi, "0.4.0", "a7966efb868b179023618d29a407548f70c52466bf1849b9e8ebd0e34b7ea11f", [:rebar3], []},
   "dialyze": {:hex, :dialyze, "0.2.1", "9fb71767f96649020d769db7cbd7290059daff23707d6e851e206b1fdfa92f9d", [:mix], []},
   "earmark": {:hex, :earmark, "0.2.1", "ba6d26ceb16106d069b289df66751734802777a3cbb6787026dd800ffeb850f3", [:mix], []},
-  "ex_doc": {:hex, :ex_doc, "0.11.4", "a064bdb720594c3745b94709b17ffb834fd858b4e0c1f48f37c0d92700759e02", [:mix], [{:earmark, "~> 0.1.17 or ~> 0.2", [hex: :earmark, optional: true]}]},
+  "ex_doc": {:hex, :ex_doc, "0.12.0", "b774aabfede4af31c0301aece12371cbd25995a21bb3d71d66f5c2fe074c603f", [:mix], [{:earmark, "~> 0.2", [hex: :earmark, optional: false]}]},
   "excoveralls": {:hex, :excoveralls, "0.5.4", "1a6e116bcf980da8b7fe33140c1d7e61aa0a4e51951cadbfacc420c12d2b9b8f", [:mix], [{:hackney, ">= 0.12.0", [hex: :hackney, optional: false]}, {:exjsx, "~> 3.0", [hex: :exjsx, optional: false]}]},
   "exjsx": {:hex, :exjsx, "3.2.0", "7136cc739ace295fc74c378f33699e5145bead4fdc1b4799822d0287489136fb", [:mix], [{:jsx, "~> 2.6.2", [hex: :jsx, optional: false]}]},
   "hackney": {:hex, :hackney, "1.6.0", "8d1e9440c9edf23bf5e5e2fe0c71de03eb265103b72901337394c840eec679ac", [:rebar3], [{:ssl_verify_fun, "1.1.0", [hex: :ssl_verify_fun, optional: false]}, {:mimerl, "1.0.2", [hex: :mimerl, optional: false]}, {:metrics, "1.0.1", [hex: :metrics, optional: false]}, {:idna, "1.2.0", [hex: :idna, optional: false]}, {:certifi, "0.4.0", [hex: :certifi, optional: false]}]},