add missing deps for example notebooks.

[sjsrey]

• mapclassify
• descartes

[codecov-io]

Codecov Report

Merging #120 (955af6d) into master (0e827ab) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #120   +/-   ##
=======================================
  Coverage   81.50%   81.50%           
=======================================
  Files          13       13           
  Lines         600      600           
=======================================
  Hits          489      489           
  Misses        111      111           

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