Arc of Gauge to expand on mouseover

I noticed that the mouseover effect of expanding and contracting was not happening with the arc gauge. I thought it was working before, and I don't know if it was taken out on purpose of left out during the refactoring of the arc portion of the code. Here is a fix that goes with the current code.
Merge branch 'patch-2' of https://github.com/bjlbernal/c3 into bjlbernal-patch-2
Merge branch 'bjlbernal-patch-2'
Update c3.min.js