Add support for GestureEvents to Sky

sky/tests/events/gesture-events.sky

+<sky>
+<import src="../resources/chai.sky" />
+<import src="../resources/mocha.sky" />
+<div id="target" />
+<script>
+describe("Gesture events", function() {
+  it("should be creatable", function() {
+    var evt = new GestureEvent("tap");
+    assert.ok(evt);
+  });
+
+  it("should be dispatchable", function() {
+    var div = document.getElementById("target");
+    var marker = false;
+    div.addEventListener("tap", function(evt) {
+      assert.isTrue(evt instanceof GestureEvent);
+      marker = true;
+    });
+    div.dispatchEvent(new GestureEvent("tap"));
+    assert.isTrue(marker);
+  });
+});
+</script>
+</sky>