Improve display of the "Country Rt Estimates" page

[joshjacobson]

• When mousing over the graph, there is an overlaying infobox that appears showing the date and case count. Please remove the year and time (20:00) from that infobox. Additionally, please add the phrase "new cases" at the end.

• If easy, please change the numeric value of new cases to display as, e.g., 42,321 rather than 42.321k. If this is time-consuming (more than an hour), it's ok not to complete this one.

• When mousing over the graph, there are overlaying infoboxs that appear showing the Estimated R, as well as and upper and lower bound. Please remove the upper and lower bound infobox displays.

• Please make the graph of daily new cases a bit more prominent, likely by increasing the brightness of that color.