styling changes Re: #275

Here are the styling changes moved to c3.css regarding #275

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.

Update c3.js, getInterporate being used to fill interpolate value. ...porate vs ...polate

Shouldn't getInterporate be getInterpolate to match what it is being used for?