Separate and test javascript travel advice utils

* Move into separate file
* Create a spec to test title to slug conversion
Don't open then collapse accordion parts

* We were using the `in` class to say that an accordion part should be
open, then collapsed all parts using JavaScript. We can simply omit the
`in` to do the same thing.
* Remove the `data-parent` attribute to allow multiple parts to be open
at once. See http://getbootstrap.com/javascript/#collapse
Create sortable parts module

* Move sortable js into a re-usable module with tests
* Add comments to indicate that it’s using jQuery UI
* Test that highlights are added and that input order is updated after
sorting