Fixed a bug in stackedArea where the seriesIndex being passed to dispatch.areaClick was not correct.

What ended up happening is, when clicking on the area, the wrong series would get selected.

src/models/stackedArea.js

@@ -160,7 +160,7 @@ nv.models.stackedArea = function() {
               point: d,
               series: d.key,
               pos: [d3.event.pageX, d3.event.pageY],
-              seriesIndex: i
+              seriesIndex: d.seriesIndex
             });
           })
           .on('mouseout', function(d,i) {
@@ -169,7 +169,7 @@ nv.models.stackedArea = function() {
               point: d,
               series: d.key,
               pos: [d3.event.pageX, d3.event.pageY],
-              seriesIndex: i
+              seriesIndex: d.seriesIndex
             });
           })
           .on('click', function(d,i) {
@@ -178,7 +178,7 @@ nv.models.stackedArea = function() {
               point: d,
               series: d.key,
               pos: [d3.event.pageX, d3.event.pageY],
-              seriesIndex: i
+              seriesIndex: d.seriesIndex
             });
           })
       path.exit().transition()