d3 example histograms

Hooked up the d3 library and added 2 histogram examples:

In app.js, control them via commenting/uncommenting this code:

<pre>
        var histogram_page = new HistogramView({collection: inmate_collection});
        router.on('route:histogram', function() {
            //simple example 1
            //histogram_page.render();

            //simple example 2
            histogram_page.render_advanced();
        });
</pre>

example 1 reads in array of numbers and draws a horizontal bar chart in SVG

example 2 reads in a json file (can easily be replaced by an API call) and draws a vertical bar chart with named labels.

Cheers!
Derek