Overview
========
Backbone.Shard is a variation on a Subset taken from different perspective. 
Shard was built as a simple "persistent filter" for collections; it can 
help grouping and displaying items of certain kind based on your filter 
function. I know it works for me, but your mileage may vary.
Usage
=====
It's easy if you're familiar with Backbone.Collection since Shard shares 
with it most of the methods marked **Underscore methods** in the 
[documentation](http://backbonejs.org/#Collection-Underscore-Methods):
    :::javascript
    var shelf = Backbone.Shard({
      collection: books,
      filter: function(book) { return book.get('read'); }
    });
    shelf.each(...);
    shelf.pluck(...);
You can add/remove models or reset *the original collection* and Shard will 
honestly try to keep up with it, but currently Shard itself has no methods 
such as add/remove/reset.
Events work and respect your filter function:
    :::javascript
    shelf.on('add', doSomething);
    collection.add({read true}); // this will call doSomething
    collection.add({read: false}); // this won't
Tests
=====
Download the 
[source](https://bitbucket.org/engored/backbone-shard/get/tip.tar.bz2) and 
open test/index.html in your browser.