BUG: add fix for opening zero observation dta files
API: Period should return NotImplemented as per the Python doc

if no comparison is implemented
Merge pull request #7379 from cpcloud/replace-no-match-7376

BUG: correct Period comparisons
TST/BUG: use BytesIO for Python 3.4 TestEncoding
Merge pull request #7388 from cpcloud/master

TST/BUG: use BytesIO for Python 3.4 TestEncoding
CLN/TST/BLD: clean up tox files [ci skip]
TST: Changed the error raised by no tables in data.io.Options

Tests were failing if the scraper got the webpage but there weren't any tables in it. Added condition to raise RemoteDataError if no tables were found.  Still IndexError if it can't find the correct table.
Merge pull request #7389 from cpcloud/update-tox

BLD/TST/DEV: update tox to use python 3.4
DOC add blanklines to release to reduce merge conflicts

Apologies if this itself causes a merge conflict!
BUG/TST: test for groupby max nan subselection bug
Merge pull request #7392 from dstephens99/OptionTests

TST: Changed the error raised by no tables in data.Options
Merge pull request #7393 from cpcloud/groupby-max-fix-6346

BUG/TST: test for groupby max nan subselection bug
ENH: add nlargest/nsmallest to Series groupby
Merge pull request #7356 from cpcloud/groupby-nlarg-smal-7053

ENH/GBY: add nlargest/nsmallest to Series.groupby
BUG: ix should return a Series for duplicate indices (GH7150)
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)