TST: Fix boxplot test for python3
ENH/CLN: add BoxPlot class inheriting MPLPlot
Merge pull request #7998 from sinhrks/boxplot

ENH/CLN: add BoxPlot class inheriting MPLPlot
Merge pull request #8098 from sinhrks/gh8091

TST: Fix boxplot test for python3
BUG: Fix Grouper with multi-level index and frequency (GH7885)