Add support for recursive inclusion of roles

[tlconnor]

This PR fixes a bug where multiple levels of role inclusion do not work.

For example, given the roles defined below, a user with role :test_role would not include the role :lowest_role.

      authorization do
        role :test_role do
          includes :lower_role
          has_permission_on :permissions, :to => :test
        end
        role :lower_role do
          has_permission_on :permissions, :to => :lower
          includes :lowest_role
        end
        role :lowest_role do
          has_permission_on :permissions, :to => :lowest
        end
      end

[almgong]

Overall looks great, but had one question about a test

[almgong]

Would there be value in checking in this test that the mock user is allowed to access the :lowest action to see that the framework supports roles that are both recursive and circular down to the lowest child?

[tlconnor]

Good idea, I have updated the test.