Add explaination of key_format to the readme

README.md

@@ -90,10 +90,25 @@ end
 json.partial! "api/comments/comments", comments: @message.comments
 ```
 
+Keys can be auto formatted using `key_format!`, this can be used to convert keynames from the standard ruby_format to CamelCase:
+
+``` ruby
+json.set_format! :camelize => :lower
+json.first_name "David"
+
+# { "firstName": "David" }
+```
+
+You can set this globaly with the class method `key_format` (from inside your enviorment.rb for example):
+
+``` ruby
+Jbuilder.set_format :camelize => :lower
+```
+
 Libraries similar to this in some form or another include:
 
 * RABL: https://github.com/nesquena/rabl
 * JsonBuilder: https://github.com/nov/jsonbuilder
 * JSON Builder: https://github.com/dewski/json_builder
 * Jsonify: https://github.com/bsiggelkow/jsonify
-* RepresentationView: https://github.com/mdub/representative_view
+* RepresentationView: https://github.com/mdub/representative_view