Switch from using a linear scale to a sqrt scale. Needs design review from Rong, but I was reading about bubble charts and scaling the radius linearly is deceiving. The sqrt scale resizes based on circle area.
Changed Y-axis to 0 - 90K
Refactored how scaling is called in Graph.js
Updated legend so largest circle is 25,000. I tried setting it to 50,000 but it didn't look good.
Closes #68