add hubVis to Suggests field in DESCRIPTION

[nickreich]

Right now there are some packages in the vignette that are not listed in the Suggests fields, e.g. hubVis (for which a specific version is required, right?), ggplot2 (although ggplot2 is Imported by hubVis, so maybe we just need hubVis?), patchwork, RColorBrewer, lubridate. I think it's possible that a few of these later packages could be removed, e.g. just put in the colors by hand and included a comment reference to RColorBrewer, and use base R to do date manipulations instead of lubridate.

[nickreich]

this is related to but not the same as Infectious-Disease-Modeling-Hubs/hubEnsemblesManuscript#19