Line drawing code relies on getClientBoundingRect() method to
compute coords and sizes of chart objects. Node uses jsdom for
browser emulation, which implements this method as a placeholder
which returns object with zero fields. To achieve proper coords
calculation, values are saved during object generation and then
they are reused for line drawing.

Animation will not be used unless transitionDuration is a positive integer.

Added transitionDuration property to chartData. Set it to 0 or null
to get rid of transition. Number values mean transition length in ms.