Get all orgs/teams/permissions in a single GitHub API call

Exposes a new API call at GitHub root level to build the complete
set of organisations and teams that current user belongs to.

This change allows to massively reduce the number of calls to GitHub 
especially for people that belongs to multiple organisations with 
lots of teams and members.

Signed-off-by: Luca Milanesio <luca.milanesio@gmail.com>
Merge pull request #112 from lucamilanesio/master

Get all orgs/teams/permissions in a single GitHub API call