#299 visible diff before save

[Branson Matheson]

So I read the 'diff' feature requests.. but this one might be simpler/easier than diff'ing at the output level. I'd like to see a visual diff since last time the user clicked save. Eg .. it'd be nice to see the rules that one changed .. visually .. before 'comitting' to a save. This might be a good *future* feature.. but would also apply right now quite nicely. Not sure if this would require a separation between the idea of a 'save' to the file and a 'commit' ( install? ) of the changes.