ENH: Add wide_to_long helper function.
ENH: Allow non-int j vals
DOC: Add wide_to_long to release notes.
CLN: expand groupby dispatch whitelist (GH5480)

- Create separate whitelists for SeriesGroupBy and DataFrameGroupBy objects
- Improve groupby whitelist testing
BUG: repr_html, fix GH5588 for the MultiIndex case
VB: add vbench for truncated repr_html
Merge pull request #5649 from y-p/PR_GH5588_again

BUG: repr_html, fix GH5588 for the MultiIndex case
DOC: minor changes in .apply section
DOC: SQL to pandas comparison (#4524)
TST: Always define fd in util/testing
DOC: cookbook update
DOC: Series.rename picking up the wrong docstring
PERF: performance regression in frame/apply (GH5654)
Merge pull request #5656 from jreback/apply_perf

PERF: performance regression in frame/apply (GH5654)
API: change _is_copy to is_copy attribute on pandas objects GH(5650)
Merge pull request #5658 from jreback/is_copy

API: change _is_copy to is_copy attribute on pandas objects GH(5650)
Merge pull request #5615 from gjreda/master

DOC: SQL to pandas comparison (#4524)
Merge branch 'wide-to-long' of https://github.com/jseabold/pandas into jseabold-wide-to-long
Merge pull request #5604 from gdraps/groupby-dispatch-part-2

Expand groupby dispatch whitelist (GH5480)
BUG: GH5398 Underscore support added for Google Analytics's new segments.
Added enhancement description for new segment support to v0.13 announcements. Found one last wrinkle in the format. Any of the valid characters can be anywhere in the string. I was too specific.