Add Mix formatter configuration

.formatter.exs

@@ -0,0 +1,11 @@
+locals_without_parens = [
+  defvocab: 2
+]
+
+[
+  inputs: ["{mix,.formatter}.exs", "{bench,config,lib,test}/**/*.{ex,exs}"],
+  locals_without_parens: locals_without_parens,
+  export: [
+    locals_without_parens: locals_without_parens
+  ]
+]

mix.exs

@@ -54,7 +54,7 @@ defmodule RDF.Mixfile do
         "GitHub" => @repo_url,
         "Changelog" => @repo_url <> "/blob/master/CHANGELOG.md",
       },
-      files: ~w[lib src/*.xrl src/*.yrl priv mix.exs VERSION *.md]
+      files: ~w[lib src/*.xrl src/*.yrl priv mix.exs .formatter.exs VERSION *.md]
     ]
   end