Support Turbolinks 5

Hi, I was hoping you could support Turbolinks 5.

I think I've found what code needs to be changed but don't do much Javascript and don't understand how this code is packaged.

I think what needs to be changed is here in index.js:

```javascript
if (typeof global.Turbolinks == 'object') {
global.document.addEventListener('page:change', function() {
Holder.run();
});
}
```

to
```javascript
if (typeof global.Turbolinks.controller == 'object') { // Turbolinks 5
global.document.addEventListener('turbolinks:load', function() {
Holder.run();
});
} else if (typeof global.Turbolinks == 'object') { // Turbolinks Classic
global.document.addEventListener('page:change', function() {
Holder.run();
});
}
```

I hope this makes sense.

Start with index.js and inspect how the JavaScript is packaged, since the issue identifies the Turbolinks integration point. Verify the behavior for Turbolinks 5 using the turbolinks:load event while preserving the existing page:change behavior for Turbolinks Classic; done means both integrations trigger Holder.run().

Written by the indexing model from the issue text.