Operations Aggregate, Average and Sum with selector
Merge branch 'AggregatorsWithSelector' of github.com:akarnokd/RxJava into pull-657-merge
Remove newly added aggregate methods

- avoiding methods with `index`
- resultSelector overload is same as `reduce(seed, accumulator).map(resultSelector)`
Rename to ReduceTest
Merge pull request #698 from benjchristensen/pull-657-merge

Merge of Pull 657: Average and Sum