Add a team model
Method to fetch repositories a user can access (not in orgs)
FetchAvailableRepositoriesJob now update teams and user_repositories
Run FetchAvailableRepositoriesJob every 3 hours
Enhance repo/teams/orgs fetching speed
Save available repo from org in UserRepository too

WARNING: there is a ugly hack, using __getattr__ and __setattr__ to get/save the fetched_at and etag fields for each organisation.

This hack will be removed when fixing #46

Also, the __getattr__ used for
"github_callable_identifiers_for_org_repositories_" can easily be
resolved by reviewing a little the way to passe parameters to fetch_many
We don't need teams for now, stop fetching them
UserRepository model becomes AvailableRepository
Save the organization name in available repositories
Update subscription page to use new available repositories
Add a "first_fetch_done" field to repositories

Better correction for #11, and needed because we now have repositories
(via AvailableRepository and Team) that are not fetched at all, but with
data got from github,so with a filed "fetched_at"
"gh" arg for GithubUser.fetch_all is optional as it will be overriden
Check subscriptions rights after checking available repositories

Fixed #24
Merge pull request #47 from twidi/available_repositories

Fetch available repositories the same way as other data