Abort a commit() if it was deemed failure by timeout.

Seems like the eval process shouldn't necessarily be interrupted.  Since the nature of the script being eval'd is unknown trying to kill it might not yield good things or perhaps it won't be killed reliably.  Of course, this means that if enough long-run scripts are eval'd then it will bring gremlin-server to its knees.
Big refactoring effort to streamline writing down the pipeline.

Removed need to have serialization selection in each handler. Pushed most serialization of responses down to the ResponseEncoder.