2.1.0 version introduced some minor BC Breaks. Here is the list:
if ('object' === typeof $('#field').parsley().isValid() && !$('#field').parsley().isValid().length) {
// field is optional and empty, nor valid, nor invalid
}
becomes
if ($('#field').parsley().isValid() && !$('#field').parsley().needsValidation()) {
// field is optional and empty, nor valid, nor invalid
}