v0.1.0

This release contains a few incompatible modifications to the CommandHandler structure:

• Rewritten CommandHandler to be a singleton. It now has a handle method that is invoked with the current state and command, returning a Results asynchronously. This allows implementations to push async actions down into the Handler class. The Results class contains most methods that previously were on CommandHandler.
• handleCommand and handleCommandAsync have been removed. Instead, CommandHandler instances can now be chained, and the chained result must be passed as a constructor argument to AbstractStatefulPersistentActor.