Save time data to element

I was needing to use the time data from this plugin for other calculations, and since it had already calculated seconds, hours, days, and years, I exposed that data along with the `datetime` in `element.data('timeago')`. I figured this was better since it was not doing all of those calculations over again.

With this, you can access the data like this (example):

```javascript
element.data('timeago').datetime // Same as usual
element.data('timeago').inWords; // 3 days ago
element.data('timeago').days; // 3
```

This also updates the tests.