Enable marking store as global, a.k.a - fallback for unknown changes.

[antitoxic]

That's an alternative to #3.

Very simple: use config to set a global: true which marks the store as default store for any uknown changes that spy() detects.

Use that store and it's associated remotedev to show those changes.

[zalmoxisus]

Looks great! Will it replace #5 or will complement that? As far as I understand, there're no problems to get the target there? For async actions we just pass the store in runInAction (which is the user's responsibility). Or there are some use case we aren't able to handle there?

[antitoxic]

I think #5 is different. There are a lot more use-cases to be done and I don't think most of them are possible. "Why not possible?" could be due to inability to get "path" or inability to find target if the observable is neither a store method nor an argument (the action could be bound to the observabe via bind() or just have access to it via external scope).

There are a lot of factors for #5. This pull request is way simpler and does the trick for most cases. I think it's good to merge because #5 has a lot more work to do.

[zalmoxisus]

Merged, will cut a release today. Thanks a lot for the contribution!

Was just wondering, whether we should close #5 or continue to work on it.