data () {
        return {
          users: [{email: 'jon@example.com'}, {email:'jane@example.com'}],
          email: 'jim@example.com'
        }
      }
As of 2.5.0 v-modeling a child of a group and a parent of that group at
the same time is no longer strictly supported. Technically it should still
work after the initial load, but never-used "feature" is a casualty of
fixing other group issues.