Initial add of the generic optimizer code
Fix scala 2.9.3 compiler crash
Improve the Rule API, and add many tests

Added tests for HMap

Actually add the tests

Get the tests passing
Add several more example optimization rules
Add a HMap constructor, per Julien's suggestion
Fix a 2.10 compile issue
A more complex example rule to prove the utility
address some review comments
Add a test, fix a bug, address some of Jco's comments
Merge pull request #537 from twitter/dag_processing

Initial add of the generic optimizer code