Add micro perf tests for existing operators

[benlesh]

From #100

• buffer (buffer(obs))
• bufferTime (bufferWithTime)
• bufferToggle (buffer(obs, fn))
• bufferWhen (buffer(fn))
• delay
• forkJoin
• mapTo (map(obj))
• multicast
• publish
• retry
• retryWhen
• skipUntil
• subscribeOn
• switchMap
• takeUntil
• toPromise
• window (window(obs))
• windowTime (windowWithTime)
• windowToggle (window(obs, fn))
• windowWhen (window(fn))
• withLatestFrom
• zipAll

[mattpodwysocki]

@Blesh maybe I'm naive here, but why is mapTo required when map for example in RxJS supports wrapping objects that are passed in.