State

Currently state (which models an event driven fsm) has a few drawbacks:

• You can't define a state machine and use it for several objects. The state machine needs to be constructed for each object. It also can't be serialized.
• There are no sub-states (not a hsm). You can emulate them using "state_substate" states, but you need to manually forward unhandled events to the parent state.
• There is no way to return to the previous state (like a pushdown automaton).