.forEach is confusingly documented

Hi there, first off, I'd just like to say that I think the work you're doing is super cool and I'm having a blast learning functional reactive programming.

It took me some time to come to the conclusion that .forEach() and .subscribe() are the same function.

This link: http://reactivex.io/rxjs/class/es6/Observable.js~Observable.html#instance-method-forEach, I get no indication that observable.subscribe() and observable.forEach() behave identically.

This link pushed me toward the conclusion: https://github.com/Reactive-Extensions/RxJS/blob/master/doc/api/core/operators/subscribe.md.

If I click on Language Specific information in : http://reactivex.io/documentation/operators/subscribe.html I get the verbatim answer that these operators are identical.

As a newbie trying to learn these things, I'd love to make a PR that:

1. More readily displays the fact that forEach and subscribe are identical operators.
2. Eliminates the confusion in the rxjs docs here

I'd love to hear thoughts from all you awesome RxJS maintainers.