More rubocop

@localshred follow up from the last PR. This gets us nearly all the way to rubocop-completeness, but more importantly, it makes the tests run again, which I broke in the last PR :(
Sure, if you feel strongly. The heuristic applied by rubocop is
```
      # This cop checks for uses of the pre 1.9 lambda syntax for one-line
      # anonymous functions and uses of the 1.9 lambda syntax for multi-line
      # anonymous functions.
```
https://github.com/bbatsov/rubocop/blob/master/lib/rubocop/cop/style/lambda.rb#L6