Make an easy way to perform side effects in response to events

[camjackson]

Something like redux thunk, but triggered by events read off the stream

[camjackson]

The basic middleware has been written, but it's not exported yet.

Right now, I still have too many questions about how it should be used. E.g., what if you only want one stream subscriber to perform a side effect (competing consumers)? What about when you restart a server and you don't want it to redo all historical side effects?

I don't want to actually export the middleware until it has meaningful docs around how to use it and how to solve these kinds of issues.

[camjackson]

Competing consumers HTTP API reference: http://docs.geteventstore.com/http-api/3.9.0/competing-consumers/