WIP: Try rubocop

Rubocop was discussed a bit a while back.  I thought I'd give it a shot.  This is a WIP trying to figure out what checks to enable/disable and whether or not we want to use it.

Feedback wanted.
I'm injecting a personal style opinion here, but I usually do an _ with no actual name when the argument is unused. I can see why this might be clearer, what do others think?