ryanb/cancan — pull request #647 by andhapp (2012-06-14 08:40:32+00:00)
Title: Fix ability precedence

The gist of this pull request can be explained via the following example:

can :manage, User, :id => user.id
cannot :destroy, User

The cannot should override and not allow the user to destroy any user. This also fixes the case where only one cannot rule is used in the ability model.