ENH: add modechoice data.
	Note: The original data is the same as in Vicent's Rdatasets.
	http://vincentarelbundock.github.io/Rdatasets/doc/Ecdat/ModeChoice.html
BUG: rename file.
Merge branch 'modechoice'
RLS: Get easy backport tool from IPython master.

RLS: Add attribution.
RLS: Update gh_api to curren IPython master.
RLS: Allow getting by milestone.
Merge pull request #1136 from jseabold/backport-tool

RLS: Add IPython tools for easier backporting of issues.