[boxplot] add support for boxplot container events

[williaster]

This PR adds the following

🏆 Enhancements

• Exposes the following props on <BoxplotSeries /> to enable more customization: containerProps, boxProps, outlierProps, minProps, maxProps, medianProps
• Adds the ability to set mouse events on the boxplot container or on its component parts (whiskers, etc)
• Consolidates some of examples for [demo][boxplot]:
  

TODO

• bump @vx/stats upon merging of boxplot container bugfix 🐛
• add tests for new functionality

[coveralls]

Coverage decreased (-0.4%) to 83.44% when pulling 6aa5d09 on chris--boxplot-fixes into f5d4f42 on master.

[coveralls]

Coverage increased (+0.7%) to 84.522% when pulling 8f7654a on chris--boxplot-fixes into f5d4f42 on master.

[coveralls]

Coverage increased (+0.7%) to 84.522% when pulling 8f7654a on chris--boxplot-fixes into f5d4f42 on master.

[coveralls]

Coverage increased (+0.7%) to 84.522% when pulling 53c58fd on chris--boxplot-fixes into f5d4f42 on master.