clean up creation of Batches in tests
Add support for more Batchers in testing
fix the tests for multiple batches
Merge branch 'develop' into scalding-batch-tests

Conflicts:
	summingbird-scalding/src/test/scala/com/twitter/summingbird/scalding/ScaldingLaws.scala
Fixes service testing for empty services
remove some braces
Merge pull request #296 from twitter/scalding-batch-tests

Scalding batch tests