Emit end event after last zoom which had an effect

#158

src/zoom.js

@@ -225,18 +225,18 @@ export default function() {
         k = Math.max(scaleExtent[0], Math.min(scaleExtent[1], t.k * Math.pow(2, wheelDelta.apply(this, arguments)))),
         p = mouse(this);
 
+    // If this wheel event won’t trigger a transform change, ignore it.
+    if (t.k === k) return;
+
     // If the mouse is in the same location as before, reuse it.
     // If there were recent wheel events, reset the wheel idle timeout.
-    if (g.wheel) {
+    else if (g.wheel) {
       if (g.mouse[0][0] !== p[0] || g.mouse[0][1] !== p[1]) {
         g.mouse[1] = t.invert(g.mouse[0] = p);
       }
       clearTimeout(g.wheel);
     }
 
-    // If this wheel event won’t trigger a transform change, ignore it.
-    else if (t.k === k) return;
-
     // Otherwise, capture the mouse point and location at the start.
     else {
       g.mouse = [p, t.invert(p)];