BUG: reading from a store with duplicate columns across dtypes would raise (GH4767)
Merge pull request #4768 from jreback/hdf_dups

BUG: reading from a store with duplicate columns across dtypes would raise (GH4767)
BUG: ensure column ordering in HDFStore with dup columns and column where specified
TST: more robust testing for HDFStore dups
Merge pull request #4769 from jreback/hdf_dups2

TST: more robust testing for HDFStore dups
PERF: faster plotting of PeriodIndex (#4705)

TST: add test for plotting PeriodSeries to SeriesPlots test
PERF: add plotting to vbench