{width} Interpolation in data-src

# tl;dr

`data-src` does not always comply with a numeric value.  
You can now replace any width breakpoint by any value of your choice.

# Features

* `{width}` can be replaced by something else than a numeric value

# Demo

A demo showcases this using Flickr URL system.

![](http://i.imgur.com/u4oBa.gif)