BUG: Bug in concatenation with duplicate columns across dtypes not merging with axis=0 (GH4771)
TST: Bug in iloc with a slice index failing (GH4771)
TST: add append/join tests for merging dup columns
BUG: join on dup columns (internally) failing
PERF: faster plotting of PeriodIndex (#4705)

TST: add test for plotting PeriodSeries to SeriesPlots test
PERF: add plotting to vbench
Merge pull request #4772 from jreback/concat_dups

BUG: Bug in concatenation with duplicate columns across dtypes not merging with axis=0 (GH4771)
TST: add dups on both index tests for HDFStore
Merge pull request #4773 from jreback/hdf_dups3

TST: add dups on both index tests for HDFStore
Merge pull request #4722 from jorisvandenbossche/slow-plotting

PERF: faster plotting of timeseries with PeriodIndex
DOC: add resample + groupby to cookbook