Favor smaller bubbles in hit.
Favor smaller bubbles in hit.

When calculating a hit on overlapping bubbles, favor the smaller bubble.
This is a simple heuristic for being fare when choosing a bubble to display
as hit. Fixes #72.

jessiejea/Flotr2,HumbleSoftware/Flotr2,beastlike/Flotr2,RobertoMalatesta/Flotr2,alanponce/Flotr2,alanponce/Flotr2,beastlike/Flotr2,RobertoMalatesta/Flotr2,nicgallardo/Flotr2,beastlike/Flotr2,jessiejea/Flotr2,HumbleSoftware/Flotr2,jessiejea/Flotr2,nicgallardo/Flotr2,alanponce/Flotr2