Fixed Typo in section: deleting all scopes in an OAuth Authorization
Renamed 'ProjectGroup' to 'Group'

This renames 'ProjectGroup' to 'Group' wherever it occurs in the
documentation, renaming our Ruby objects as well to avoid confusion.
Remove Basic Authentication Support from specification.

Unless it is considered necessary at a later date, we are removing
Basic Authentication Support from version 2 of the Freckle API.
Instead, consumers should use OAuth2.