Applying Aggregator in Aggregate execution

First try.

Some test errors, but matches with another baseline result. Will double
check whether all test cases can be passed currently later.

Error info below:
[info] Passed: Total 197, Failed 0, Errors 0, Passed 195, Skipped 2
[error] (repl/test:test) sbt.TestsFailedException: Tests unsuccessful
[error] (streaming/test:test) sbt.TestsFailedException: Tests
unsuccessful
[error] (core/test:test) sbt.TestsFailedException: Tests unsuccessful
[error] Total time: 1755 s, completed May 1, 2014 10:49:27 PM