Upgrade Credo to version 0.6.0 (#200)

This also disables the "Readability.Specs" check because it appears to
crash Credo when it encounters some of our macro-ized code. That can be
investigated separately.

.credo.exs

@@ -31,6 +31,7 @@
       {Credo.Check.Readability.ModuleNames},
       {Credo.Check.Readability.ParenthesesInCondition},
       {Credo.Check.Readability.PredicateFunctionNames},
+      {Credo.Check.Readability.Specs, false},
       {Credo.Check.Readability.TrailingBlankLine},
       {Credo.Check.Readability.TrailingWhiteSpace},
       {Credo.Check.Readability.VariableNames},

mix.exs

@@ -66,7 +66,7 @@ defmodule Thrift.Mixfile do
   defp deps do
      [{:ex_doc, "~> 0.14", only: :dev},
       {:excoveralls, "~> 0.6", only: [:dev, :test]},
-      {:credo, "~> 0.5", only: [:dev, :test]},
+      {:credo, "~> 0.6", only: [:dev, :test]},
       {:dialyxir, "~> 0.4", only: :dev, runtime: false},
       {:benchfella, "~> 0.3", only: [:dev, :test]},
       {:connection, "~> 1.0"},

mix.lock

@@ -1,8 +1,8 @@
 %{"benchfella": {:hex, :benchfella, "0.3.3", "bbde48b5fe1ef556baa7ad933008e214e050e81ddb0916350715f5759fb35c0c", [:mix], []},
-  "bunt": {:hex, :bunt, "0.1.6", "5d95a6882f73f3b9969fdfd1953798046664e6f77ec4e486e6fafc7caad97c6f", [:mix], []},
+  "bunt": {:hex, :bunt, "0.2.0", "951c6e801e8b1d2cbe58ebbd3e616a869061ddadcc4863d0a2182541acae9a38", [:mix], []},
   "certifi": {:hex, :certifi, "0.7.0", "861a57f3808f7eb0c2d1802afeaae0fa5de813b0df0979153cbafcd853ababaf", [:rebar3], []},
   "connection": {:hex, :connection, "1.0.4", "a1cae72211f0eef17705aaededacac3eb30e6625b04a6117c1b2db6ace7d5976", [:mix], []},
-  "credo": {:hex, :credo, "0.5.2", "92e8c9f86e0ffbf9f688595e9f4e936bc96a52e5606d2c19713e9e4d191d5c74", [:mix], [{:bunt, "~> 0.1.6", [hex: :bunt, optional: false]}]},
+  "credo": {:hex, :credo, "0.6.0", "44a82f82b94eeb4ba6092c89b8a6730ca1a3291c7940739d5acc8806d25ac991", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, optional: false]}]},
   "dialyxir": {:hex, :dialyxir, "0.4.0", "53ac3014bb4aef647728a697052b4db3a84c6742de7aab0e0a1c863ea274007b", [:mix], []},
   "dialyze": {:hex, :dialyze, "0.2.1", "9fb71767f96649020d769db7cbd7290059daff23707d6e851e206b1fdfa92f9d", [:mix], []},
   "earmark": {:hex, :earmark, "1.0.3", "89bdbaf2aca8bbb5c97d8b3b55c5dd0cff517ecc78d417e87f1d0982e514557b", [:mix], []},