Generate county-level information from IHME forecasts

[lossyrob]

The goal of this issue is to produce a GeoDataFrame of county-level predictions based on the IHME forecast data. The IHME data is state-level, and will be so until enough input data is available to allow their methods to be applied to that spatial resolution.

Before they put out county-level information, we can estimate county forecasts by doing spatial disaggregation of the state data. E.g. info for spatial disaggregation -http://www.integrated-assessment.eu/eu/guidebook/spatial_disaggregation.html

Deriving county-level predictions in this way will surely introduce error, so approaches should be discussed and fact that these are not estimates from IHME and the methods for deriving the data should be made very clear in the documentation.