Can't use createObservableMethod with RxJS 6

[zero298]

It looks like createObservableMethod will fail because of how it checks to see if share() is supported here.

if (!Rx.Observable.prototype.share) {...}

Right now, it is checking for support on the prototype of Observable when share() is actually somewhere around RxJS.operators.share(). Is there a way to address this through the new piping mechanism without having to utilize the rxjs-compat module?

This is sort of related to #69 but since createObservableMethod directly uses share() off the Observable prototype, the feature is broken.

[regou]

#83