choropleth improvements

[Kully]

addresses: #944

Also does:

• enhancement from rename offline_mode param from ff.create_choropleth #944
• Turns off hover for the lines. It fights with hover for the centroids.
• Turns on persistent selection api for the centroid points, so that the centroids are invisible until you select, then they show up in white with a thin border.
• 0-pad the 4 digit FIPS numbers of the legend

[Kully]

ready for a review when tests pass
cc: @cldougl @jackparmer

Perhaps this should also be version 2.5.0 Chelsea?

[jackparmer]

💃 from me

[Kully]

@cldougl

[cldougl]

@Kully I don't think the package data should be added in the test directory: https://github.com/plotly/plotly.py/tree/master/plotly/tests/test_optional/test_figure_factory

don't you want to be testing that the package data is read properly from: https://github.com/plotly/plotly.py/tree/master/plotly/package_data ?

[cldougl]

re: #947 (comment)
👍 yep version 2.5.0

[cldougl]

💃