Added WHO Situation Report 1-24 data for SARS-CoV-2 outbreak (COVID-19)

[eebrown]

I've added the WHO Situation Report data. I modified the variable names to be consistent with your package. I've got a small script I can run to update it from my original data, so I can keep it updated from time to time.

[finlaycampbell]

This is great, thanks. Could you make two small changes before I merge the pull request?

1. Change the version number to 1.8, because this is adding a new 'feature'
2. Resave your .RData file using version = 2 in your save call. I'm getting the following warning and we want to keep the current R dependency:

     WARNING: Added dependency on R >= 3.5.0 because serialized objects in  serialize/load version 3 cannot be read in older versions of R.  File(s) containing such objects:  'outbreaks/data/sarscov2_who_2019.RData'

[eebrown]

Great, think it should be good now. I'll push an update from time to time. This is how to easily use my other package as "upstream" for the data object here: https://gist.github.com/eebrown/3f25afe42ed126803be819940356c0b7

[finlaycampbell]

Great, thanks a bunch!