TokenFlow 1.0 Beta

In this Release:

1. Added an event system that allows users to easily monitor progress or build components like progress bars.
2. Changed the result type when a user function throws an error. Now, if an exception is thrown in the request function, an UnexpectedUserException(error_str, traceback_str) object will be returned as the request result.

Things to note:

1. The user's request function should now return a triple—in addition to the action and result from previous versions, an event payload must also be returned. This payload will be passed to the callback function in the event system. If not needed, None can be returned as the event payload.