Tempo Implementation

[AndersJensen-NOAA]

This PR replaces #245

[grantfirl]

@AndersJensen-NOAA Is this the final PR? It makes it very difficult to review this when new PRs replace old ones. For example, in order to see what comments were addressed from #245, I have to go back and forth between that one and this one and check for changes manually. If you had just made your changes in #245, it would have been much easier to continue reviewing this because GitHub highlights changes for you.

[AndersJensen-NOAA]

@AndersJensen-NOAA Is this the final PR? It makes it very difficult to review this when new PRs replace old ones. For example, in order to see what comments were addressed from #245, I have to go back and forth between that one and this one and check for changes manually. If you had just made your changes in #245, it would have been much easier to continue reviewing this because GitHub highlights changes for you.

@grantfirl Yes, this is the final PR. Apologies for the continued replacement PRs. The issue mentioned in this discussion
NOAA-EMC/fv3atm#923
tripped me up for so long (several days) that I decided to start over and rebuild the PR in one sitting, piece by piece to track it down.