RxJS Observable support

[LAJW]

I want to add support for custom collections/streams (Observable, fetch, etc.). Some can be built-in as optional dependencies, but there should be also a way for the user to add custom overloads.

Something like this:

const reduce = require("co-reduce-any").overload([
  [
    collection => collection instanceof Observable,
    (observable, generator) => { ... }
  ],
  [ secondTypeCheck, secondOverload ],
  ...
])

So when reduce() is issued, before jumping straight to enumerating keys in objects, we would first check if there was defined a custom overload.

I'd like to first take care of Fugazi, so if anyone wants to do this, fork ahead.