staltz/rxmarbles — pull request #4 by cristinecula (2014-10-15 09:36:30+00:00)
Title: Added aggregate example

First of all let me say that I love rxmarbles! It has helped me alot in understanding how rxjs observables work.

I think that aggregate is not simply a clone of scan, since it emits only the final value of the aggregation. I found this extremely useful after doing a groupBy to create another stream where the groups are reduced to single values with accumulated properties:

```
.groupBy (log) ->
log.day
.flatMap (group) ->
group.aggregate (acc, log) ->
acc.downtime += log.downtime
acc
```

Therefore I think this transformation deserves it's own place in the examples.