The validator element() method delegates to check(). When check() is
passed a radio or checkbox input element (call it 'A'), it instead
checks the first element with the same name in the form (call it 'B').
If element B is judged invalid, a bug occurs. Element A will have been
added to the currentElements array, but element B is what is added to
the errorList. So, when showErrors is called, element A will be in
validElements(), and will be unhighlighted.
This is fixed by having element() also change its target to be the
first element of the same name when passed a checkbox or radio input.
Signed-off-by: Eric Naeseth <eric@thumbtack.com>
