Two questions about the comparator's return values:

1. For every resolution, we return the log of the delta between the two inputs (example here). This makes sense to me at the seconds resolution, where the distance is often very large, but is it also the right call for days, months, and years?

2. We're taking the log of the difference (log(x - y)) as opposed to the difference of the logs (log(x) - log(y)). I'm unclear on the theory behind this choice so I don't know if it matters, but it's technically different than the example in the price comparator, which I based this calculation on. Is it fine like this?

Curious to hear your thoughts @fgregg. I won't be working on this until Tuesday, so no rush.

Seems like there is some circumstances where these are not behaving as expected when just using the parse_resolution method. Lets write some tests.