Merge pull request #7402 from jreback/ix_series

BUG: ix should return a Series for duplicate indices (GH7150)
BUG: Bug in multi-index slicing with incomplete indexers (GH7399)
TST7337: Disallow use of dateutil tzfile objects whose filename contains '.tar.gz'.
TST7337: Fix test failures on windows.

Avoid constructing dateutil timezones explicitly because of filename issue.
Use dateutil.tz.tzutc() to construct UTC timezone instead of
dateutil.tz.gettz('UTC')
Update docs to reflect this.
Tidy up examples in the timezones section of the docs.
BUG: Bug in multi-index slicing with a step in a sliced level (GH7400)
Add test for conversion between dateutil.tz.tzutc() and dateutil.tz.gettz('UTC')
Merge pull request #7404 from jreback/mi_indexing

BUG: mi indexing bugs (GH7399,GH7400)
BUG/OUTPUT: fix repring of MI nat

Fix neg indexers in datetimeindex
Merge pull request #7362 from ahlmss/windows_tests

TST7337: Fix test failures on windows.
Merge pull request #7410 from cpcloud/nat-index-first-take-7406

BUG: fix repring of nat multiindex and fix neg indexing in datetimeindex
make nanops._maybe_null_out work with complex numbers ( issue #7353 )
support axis=None for nanmedian ( issue #7352 )
make nanops work when ndim==1 and axis==0 ( issue #7354 )
Make nanops._has_infs work for additional dtypes and multidimensional arrays ( issue #7357 )
add tests for nanops
minor nanops pep8 fixes
support more datetime64 and timedelta dtype variants
also disallow timedeltas for objects that disallow datetime64