fix unidoc target

The ./sbt unidoc target is failing with errors like

[error] /Users/fkaelin/workspace/github/summingbird/summingbird-storm/src/main/scala/com/twitter/summingbird/storm/option/SummerOptions.scala:42: OnlineSuccessHandler is already defined as value OnlineSuccessHandler
[error] case class OnlineSuccessHandler(handlerFn: Unit => Unit)

There are duplicate type definitions in the online and storm packages, which compiles fine due to shadowing but the docs don't seem to like that. With this change the unidoc target succeeds (I want/need it as I use Dash for documentation browsing)

Not sure this is the right way to go about it, ./sbt test failed with a java.lang.OutOfMemoryError: Java heap space. There is also duplicate code in https://github.com/twitter/summingbird/blob/cbfb833e78fd6434bc1cfe18ce0696e8cf527bee/summingbird-builder/src/main/scala/com/twitter/summingbird/builder/package.scala#L66 that points to the storm options I am deleting - which makes me wonder why ./sbt compile still succeeds.