stevage Correct promise.tap "equivalent" explanation
I'm far from certain about this, but I don't think the "equivalent" JS code for `promise.tap` was correct.

According to the description of the function, `promise.tap` should wait for `doSideEffectsHere`'s return, and should reject if `doSideEffectsHere()` returns a rejected promise. Which the "equivalent" code didn't achieve. I think.
Latest commit 3d2b25f Feb 15, 2016