urltools for Everyone

#1445 is great, if you use node.  For those that don't this should mean we can find a reasonable fallback.
Users can force urltools to use a specific system by setting `URLTOOLS_METHOD` to one of:
* `node`
* `python`
* `ruby`
* `php`
* `perl`

Note that you can't (currently) choose which `perl` sublibrary to use, it will use either `URI::Encode`, `URI::Escape`, or regular expressions in that order of preference.