Update release notes with breaking changes

Author: ayoung

releasenotes.markdown

@@ -3,9 +3,19 @@
 ## 104.0
 
 * Fixed Windows Phone and Silverlight to use culture when calling Convert.ChangeType() (thanks trydis)
-* Added support for non-standard HTTP methods (thanks jhoerr)
+* Added support for non-standard HTTP methods (thanks jhoerr)  
+  New API methods include:
+  * IRestClient.ExecuteAsyncGet()
+  * IRestClient.ExecuteAsyncPost()
+  * IRestClient.ExecuteAsyncGet<T>()
+  * IRestClient.ExecuteAsyncPost<T>()
+  
+  See [groups discussion](https://groups.google.com/forum/?fromgroups=#!topic/restsharp/FCLGE5By7AU) for more info
+
 * Resolved an xAuth support issue in the OAuth1Authenticator (thanks artema)
-* Change AddDefaultParameter methods to be extension methods (thanks haacked)
+* Change AddDefaultParameter methods to be extension methods (thanks haacked)  
+  Added RestClientExtensions.AddDefaultParameter() with 4 overloads. See pull request [#311](https://github.com/restsharp/RestSharp/pull/311) for more info
+
 * Adding support for deserializing enums from integer representations (thanks dontjee)
 
 ## 103.4