use 2.2.0 in the readme example

Zensavona · Zensavona · commit 16fd87992ab8 · 2018-12-13T15:08:41.000+07:00
diff --git a/README.md b/README.md
@@ -16,7 +16,7 @@ Add the following to your `mix.exs`
 ```
 
 defp deps do
-  [{:domainatrex, "~> 2.1.6"}]
+  [{:domainatrex, "~> 2.2.0"}]
 
 ```
 
