Update readme with date to words

Changed the readme to add date-to-words documentation.

readme.md

@@ -885,7 +885,7 @@ Passing `wordForm` argument in when it is not applicable will not make any diffe
 ```
 
 ### <a id="date-time-to-ordinal-words">DateTime to ordinal words</a>
-This is kind of an extension of Ordinalize
+This is kind of an extension of ToWords and Ordinalize
 ```C#
 // for English UK locale
 new DateTime(2015, 1, 1).ToOrdinalWords() => "1st January 2015"