Fix #237 add data-driven color to Polar Plot marker color

[jmonticolo]

To resolve the issue #237, in addition to add data-driven size for the polar plot marker, I updated the code.

To make the file closest to scatter.py, I converted dict( into { for the graph_objs constructor.

[ghtmtt]

there are still some issues to solve with the data-dirven color ramp, but not related with this PR. I tested it and it works like for the other plot types.

Many thanks for the contribution!