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