Fix MarketMap coloring issue
Fix MarketMap coloring issue

Calling `map` on a TypedArray returns an array of the same type,
resulting in the variable `mapped_data` being an Int32Array containing
zeros instead of an array of objects. This caused coloring issues
because the data linked to each rectangle was wrong.

bloomberg/bqplot,SylvainCorlay/bqplot,dmadeka/bqplot,bloomberg/bqplot,bloomberg/bqplot,SylvainCorlay/bqplot,ChakriCherukuri/bqplot,ChakriCherukuri/bqplot,SylvainCorlay/bqplot,ChakriCherukuri/bqplot,dmadeka/bqplot