Make hover tooltips describe more details

[nsunami]

The tooltips that will show on hover are showing redundant/no information to the plot.

We want to make the tooltips more descriptive. For example, the tooltip for the following view should show..

"In New Castle County, there are 28,486 families spending 30% or more of their income on rent."

We want to make sure that the tooltips are descriptive across the visuals and the map.

Charts that need work:

• [x] Pie chart (fixed via #190)
• [ ] Count chart (fixed via #194)
• [x] Proportions across counties (fixed via #175)
• [x] Map
• [x] Explore - Bar chart showing proportions
• [x] Explore - Bar chart showing the ranks of the selected tracts

[mehak25]

Map hover shows census tract. Pop-up is not looking good on the map because we reload the map at every click and therefore popup disappears as soon as the map reloads.