docs: update README info

BREAKING CHANGE
This release changes to a different underlying class system - which should not have any user
visible issues other than there are now no longer the full set of basic methods on an object
that the old ClassForge base gave.  Additionally the classes are generated from the Broadworks
R24 schemas.

README.md

@@ -17,7 +17,7 @@
 - python objects to match all Broadworks schema objects
 - API framework to talk to a Broadworks server
 - additional magic to handle authentication and sessions
-- Based on Broadworks schema R21
+- Based on Broadworks schema R24
 
 ## Current Version
 
@@ -52,9 +52,22 @@ response = api.command("SystemSoftwareVersionGetRequest")
 print(response.version)
 ```
 
+## Version 2
+
+Despite the bump in version number there are no known major incompatibilities
+from previous versions.  However the underlying class base has been changed
+to a vanilla python slots based system - the thinking behind this is in the
+API internals documentation.  This will change the underlying requirements.
+
+Additionally at the same time I have converted to Broadworks R24 API schema
+files as the basis for generating these classes.
+
+
 ## Credits
 
-The class is built using Michael DeHaan's [`ClassForge`](https://classforge.io/) object system.
+The class used to be built using Michael DeHaan's [`ClassForge`]
+(https://classforge.io/) object system, however from version 2.0.0 it has
+been based on vanilla python slotted objects.
 
 Development on the python version was done by
 [Nigel Metheringham `<[email protected]>`](https://github.com/nigelm/)