Pie chart gives console error when changing number of segments is animated

[mcnuttandrew]

The pie chart yields a bunch of console errors like this

d3.js:8756 Error: Invalid value for <path> attribute d="M109.35191368826634,412.2430898706445A426.5,426.5 0 0.000006912,1 -225.26700899816143,362.14965805466653L-144.9842766002235,233.08532321974673Z"

when animation is on and the number of segments is increasing or decreasing. This doesn't appear to affect the functionality of the chart, but is a little worrisome.

[chrisirhc]

Marking this for a later release since it doesn't affect functionality.

[bulyonov]

Apparently d3 is a source of problems here: it is not able to animate arcs from the initial state without the d property.

[bulyonov]

Further investigation showed d3 generates a proper d property for an arc, but is not able to do a good interpolation of that (arcs have certain restrictions in values)

[bulyonov]

Fixed in #126