label-matches.js should return gracefully if no type is present

[downzer0]

In the label-matches.js file, if no type attribute is present on the element, the results crash. While not common, an <input /> is possible so this should return gracefully in that event.

Suggestion:

if (node.nodeName.toLowerCase() !== 'input') {
  return true;
}
if (!node.getAttribute('type')) {
  return true;
}
var t = node.getAttribute('type').toLowerCase();
var types = [
  'hidden',
  'image',
  'button',
  'submit',
  'reset'
];
if (types.indexOf(t) !== -1) {
  return false;
}
return true;

[marcysutton]

That seems easy enough. Would you be interested in submitting a PR?