Changed general.groupby to return an OrderedDict
Implemented a DamageWriter class
Renamed the dmg keys to be consistent with the engine
Code cleanup
Fixed ordering on the Site objects
Refactored the scenario_damage QA tests
Added docstrings per the DamageWriter class
Added an .apply method to AccumDict
Fixed a docstring
Merge pull request #93 from gem/DamageWriter

Added a DamageWriter class and the expected outputs for the ScenarioDamage QA tests