Validating group of checkboxes (at least one required)

[iamkeir]

Possibly not bug, maybe just limitation - validating a group of checkboxes where at least one is required: https://codepen.io/iamkeir/pen/jgzOJr?editors=1010

However, if you assign values to the checkboxes, the above starts outputting multiple error messages... which seems odd: https://codepen.io/iamkeir/pen/wVmKyV?editors=1010

Possibly related to #17?

[xini]

see #40