resolves #193: simpler commit tables

@kevgo 

Can now remove the duplication from all commit tables. I removed them from just git-extract for now. Will remove it from the others, but wanted to give you a chance to look at it now.
* I think you are monkey-patching the Hash class here, so say that.
* Classes in Ruby are capitalized
* This comment is for the whole file, so add two empty lines after it.