API Suggestion: rx

[dazraf]

Fantastic module, thanks!
I use the async version. The callbacks aren't composable / chainable.
So I've ended up writing extension methods wrapping all existing methods on MongoCollection, to return rx-java equivalents: Single, Observable.
Would be great if KMongo could provide similar.

[zigzago]

I would prefer not to add a java-rx dependency on kmongo-async.
It would be nice to create a kmongo-async-rx subproject with the rx extensions methods.

Could you submit a PR, or send to me the extension methods you use?
Thanks

[dazraf]

Good idea. Will share you my extensions and you can integrate into a new module if you like.