Allow multiple connections inside A0Strategy.
Add A0Connection class.
Start using A0Connection instead of NSDictionary.
Cleanup A0Application interface.

Have a property for database strategy and another for all social ones.
Add strategy type to A0Strategy.
Filter strategies in application.
Add method to retrieve strategy by its name.
Removed unnecesary parameter.
Refactor how A0APIClient should be used.

Removed neccesity to fetch A0Application before using client.
Social authentication now requires connection name.
Database auth will fetch connection name from application if loaded (otherwise
it must be provided as a parameter).
Fail when no connection name provided in DB auth
Removed unused errors.
Merge pull request #33 from auth0/chore-multiple-connections

Multiple connections per Strategy.