BUG: fix period index object instantiation when joining with self
Merge pull request #4379 from cpcloud/self-join-index-is-same

BUG: fix period index object instantiation when joining with self
Fixed issue #4345.
Merge pull request #4360 from nfoti/master

Fix issue #4345: graphics test failure
Fix an issue with the csv cparser when usecols is used
Merge pull request #4406 from tr11/fix_csv_parser_dtypes

BUG: Fix an issue with the csv cparser when usecols is used
BUG: Fix an issue in merging blocks where the resulting DataFrame had partially set _ref_locs (GH4403)
Merge pull request #4410 from jreback/df_rename

BUG: Fix an issue in merging blocks where the resulting DataFrame had partially set _ref_locs