Focus: pending/complete

[martinthomson]

@hober notes in #49:

As an overall comment: I think we're unlikely to need the complexity/granularity of the Focus: $FOO (pending)/Focus: $FOO (complete) labeling system, and we're unlikely to actually do it. Too many fiddly bits.

Originally posted by @hober in #49 (comment)

This pending/complete thing predates that change, so it's worth opening a new issue to discuss it. I agree with the sentiment above: tracking whether something is complete or not with labels sounds neat, but in practice I suggest that it would be easier to:

1. Mark things with focus areas.
2. Before closing, manually verify that an appropriate level of review in each of those areas has been provided.

The value of labels lies in the support they provide for process, but each additional transition adds overhead. That overhead seems unnecessary in this case.