As part of the removal of jQuery from the annotator, remove usage from
`range.js`:

 - Replace `parents()` method with a small helper function

 - Rewrite `getTextNodes` function to accept and return DOM nodes rather
   than jQuery collections

 - Use `Node.contains` instead of jQuery's `contains` method. Note that there
   is a semantic difference that `contains(nodeA, nodeA)` returns
   `false` whereas `nodeA.contains(nodeA)` returns `true`. This enabled
   simplifying a condition.