fix data order of tooltip

Gruntfile.coffee

@@ -92,7 +92,7 @@ module.exports = (grunt) ->
               specs: 'spec/*-spec.js'
               helpers: 'spec/*-helper.js'
               styles: 'c3.css'
-              vendor: 'https://raw.githubusercontent.com/mbostock/d3/v3.5.0/d3.min.js'
+              vendor: 'https://rawgit.com/mbostock/d3/v3.5.0/d3.min.js'
 
         uglify:
           c3:

spec/tooltip-spec.js

@@ -98,4 +98,25 @@ describe('c3 chart tooltip', function () {
             expect(left).toBe(leftExpected);
         });
     });
+
+    describe('tooltip getTooltipContent', function () {
+	beforeAll(function () {
+            tooltipConfiguration = {
+		data_order: 'desc'
+	    };
+        });
+
+	it('should sort values desc', function () {
+	    var eventRect = d3.select('.c3-event-rect-2').node();
+            window.setMouseEvent(chart, 'mousemove', 100, 100, eventRect);
+
+            var tooltipTable = d3.select('.c3-tooltip')[0];
+	    var expected = ["", "c3-tooltip-name--data3",
+			    "c3-tooltip-name--data1", "c3-tooltip-name--data2"];
+	    var i;
+	    for (i = 0; i < tooltipTable[0].rows.length; i++) {
+		expect(tooltipTable[0].rows[i].className).toBe(expected[i]);
+	    }
+	});
+    });
 });

src/tooltip.js

@@ -30,6 +30,17 @@ c3_chart_internal_fn.getTooltipContent = function (d, defaultTitleFormat, defaul
         nameFormat = config.tooltip_format_name || function (name) { return name; },
         valueFormat = config.tooltip_format_value || defaultValueFormat,
         text, i, title, value, name, bgcolor;
+    
+    if (config.data_order === 'desc') {
+	d.sort(function(a,b){
+	    return b.value-a.value;
+	});
+    } else if (config.data_order === 'asc') {
+	d.sort(function(a,b){
+	    return a.value-b.value;
+	});
+    }
+    
     for (i = 0; i < d.length; i++) {
         if (! (d[i] && (d[i].value || d[i].value === 0))) { continue; }