JoinerImpl.join_array_data
JoinerImpl.promote_private_data to promote_data

Realized that there was nothing inherently special about the "private" key,
and that it might be handy to promote data corresponding to other keys as
well, specifically promoting data from site.data['hub'] to site.data.
JoinerImpl.remove_private_data to remove_data

Realized that there was nothing inherently special about the "private" key,
and that it might be handy to remove data corresponding to other keys as well.
Bugfix: promote Hash data recursively
Update create_team_by_email_index()

Also removes join_public_data().
JoinerImpl.join_data()

Also replaces join_private_data() implementation with a call to join_data().
Switch over to consolidated data-private format
Tweaks per @afeld's comments in #14
Merge pull request #14 from 18F/team-data-private-3

Switch over to consolidated data-private format