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?

Added chart_arc_gauge.html as a sample/demo of functionality. Added c3.update function to update configurations in the demo.

Added chart_arc_gauge.html as a sample/demo of functionality. Added c3.update function to update configurations in the demo.

Merged upstream to 0.1.42, conflicts resolved; Fixed errors with rectW function where __interaction_enabled block exists in redraw function.