Upgrade dev dependencies

Author: r8

mix.exs

@@ -46,8 +46,8 @@ defmodule OEmbed.Mixfile do
       {:exvcr, "~> 0.9", only: :test},
       {:inch_ex, ">= 0.0.0", only: :docs},
       {:earmark, ">= 0.0.0", only: :dev},
-      {:ex_doc, "~> 0.16", only: :dev, runtime: false},
-      {:credo, "~> 0.8", only: [:dev, :test], runtime: false}
+      {:ex_doc, "~> 0.19", only: :dev, runtime: false},
+      {:credo, "~> 1.0.0", only: [:dev, :test], runtime: false}
     ]
   end