Da Bubbles

Python side
* Make the lat/lon in the pre-rendered geojson doubles (instead of strings). This makes it so that, when they are rendered, they don't need to be converted to floats
* Also include total # of houses in the hmda api

JS side
* Most heavy lifting is around reworking a few functions to account for *multiple* layers/data sources
* Url param parser to fetch lender id
* Expanded `draw` function to draw circles (if rendering the loanVolume layer)
* When rolling over bubble, show metrics in the left-bottom corner (as we do with tracts)
The rest of this looks good. However, I think I understand the need for this styling to be here - but is there a way to extract that away? I suppose because we're in visualizations the logic for how to display things and what they look like are intertwined. However, that just seems like it might get us into to trouble later? Not sure how to thing about this.