Introducing a state manager to zflow's architecture.

[darmie]

So I have been thinking that zflow is a mess because of how it attempts to mirror Noflo's implementation which took advantage of Javascript's shared memory, simple callback system and promises.

Events on the graph could be managed and dispatched by a state machine like redux; this can make the code base cleaner, and allow editors and runtimes to subscribe to the graph state without tight coupling.