DC.js - axis margins

HTML

<script src="//cdnjs.cloudflare.com/ajax/libs/d3/3.4.9/d3.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/crossfilter/1.3.7/crossfilter.js"></script>
<link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/dc/1.7.1/dc.css">
<script src="//cdnjs.cloudflare.com/ajax/libs/dc/1.7.1/dc.js"></script>
<h1>Top Oil Reserves</h1>
<div id="chart"></div>

JavaScript

var chartExample = {
    
     
    initChart: function (data, countries) {

        var ndx = crossfilter(data),
            countryDimension = ndx.dimension(function (d) {
                return d.name;
            }),
            countryGroup =  countryDimension.group().reduceSum(function(d) { return d.sale; }),
            chart = dc.barChart("#chart");

        chart
          .height(300)
          .width(800)
          .dimension(countryDimension)
          .group(countryGroup)
          .x(d3.scale.ordinal().domain(countries))
          .xUnits(dc.units.ordinal)
          .xAxisLabel("MMbbl = one million barrels")
          .yAxisLabel("Reserves (MMbbl)")
          .elasticY(true);
        
        chart
        .renderlet(function(chart){
            debugger;
        var colors = d3.scale.ordinal().domain(countries)
            .range(["steelblue", "brown", "red", "green", "yellow", "grey", "blue", "black"]);
        chart.selectAll('rect.bar').each(function(d){
             d3.select(this).attr("style", "fill: " + colors(d.data.key));
    });
        
});
        
        dc.renderAll();
    },
    initData: function () {
        var countries = ["Venezuela", "Saudi", "Canada", "Iran", "Russia", "UAE", "US", "China"];
        var allData =[
          {name:'Venezuela',sale:300},
          {name:'Saudi',sale:253},
          {name:'Canada',sale:150},
          {name:'Iran',sale:125},
          {name:'Russia',sale:110},
          {name:'UAE',sale:90},
          {name:'US',sale:40},
          {name:'China',sale:37}
        ];
        chartExample.initChart(allData, countries);
    }
};

chartExample.initData();