Whisker plot, with a dashed line for delta

[mccalluc]

Don't even worry about connecting it to any particular data, but just figure out which charting library to use to so we can have:

• whiskers on the bars
• dashed horizontal line across the full width
• perhaps grey-out the bars below that line
• no labels on vertical axis. (With mock data, the absolute number of counts wouldn't matter, so we don't want to label the axis.)

[cmbz]

One possibility? https://seaborn.pydata.org/generated/seaborn.boxplot.html