Fix scaladoc link.
multi module.
Merge pull request #302 from twitter/multi_module

Multimodule support for Scalding's SBT build
Merge pull request #320 from twitter/feature/doc_link

Fix ScalaDoc Link in README.
add scalding date and scalding args.
Merge pull request #321 from twitter/feature/scalding_date_args

Pull out scalding-date and scalding-args.