BBC-News/Imager.js — pull request #68 by BPScott (2014-01-05 16:27:22+00:00)
Title: [Fix #67] Add `widthInterpolator` option

This allows the widthsMap to be dynamically created using an array of
availableWidths and a function, rather than having to build an
availableWidths object outside of Imager.

This allows you to do this:

```html

```

```js
new Imager('.delayed-image-load-16x9', {
availableWidths: [160, 240, 320, 480, 560],
widthInterpolater: function(w){ return w + 'x' + (i / (16/9)); }
});
```
To build a url that looks like: http://ichef.bbci.co.uk/images/ic/160x90/p01mzt0r.jpg