Thinking about this some more, I think we can get the best of both worlds if we're careful about this.  Ideally, formatters would not have to have separate handling for pending vs skipped, and could just have the current handling for pending apply to both.  However, if they want to treat them differently, we should provide a mechanism to do so.  I think the way to do this is to keep the single formatter notification of `example_pending` with the same existing metadata keys, and add a new metadata key which is `pending_type` which could either be `:pending` or `:skipped` -- that way, within the `example_pending` notification a formatter can differentiate and treat it differently if it wants, but otherwise formatters can treat them the same.