Allow specifying a user_store in config.
When a user is in an unknown state, push them to the start state rather than raising an error and locking them out of the application entirely.
Better description in message logged when an unknown state is encountered.
Add tests for new handling of unknown states in switch_state.
Remove unused done parameter from load_user.
Add tests for loading and saving users.
Don't assume that results of store_user and load_user fire synchronously (the do currently for the dummy_api, but someday the dummy_api might become async which would be cool).
Merge branch 'feature/issue-15-namespace-states-properly' into develop