update readme to reflect which portions of the spec we support

Author: justincy

README.md

@@ -3,5 +3,5 @@
 [JSON Schema](http://json-schema.org/) for [GEDCOM X](http://www.gedcomx.org/).
 Pairs nicely with validation tools such as [tv4](https://github.com/geraintluff/tv4).
 
-This currently only supports the GEDCOM X Conceptual Model JSON format. It does
-not yet support the GEDCOM X RS or Records spec.
+This supports the GEDCOM X Conceptual Model, RS, Atom Extensions, and Records 
+specs in JSON format.