Update moveToObject.js

Guess I stumbled upon a bug. This is my first github bugfix attempt :)

So I'm not entirely sure this works, because I don't use mobile testing yet, but this seems more like what the description is saying:
Default: move to center of the element
When offset is set: move to left top of the element + offset

Can someone verify + test this?

Thanks!
Daan

lib/commands/moveToObject.js

@@ -45,12 +45,12 @@ module.exports = function moveToObject(selector, xoffset, yoffset) {
                 });
             });
         }).then(function(res) {
-            var x = res.location.value.x,
-                y = res.location.value.y;
+            var x = res.location.value.x + (res.size.value.width / 2),
+                y = res.location.value.y + (res.size.value.height / 2);
 
             if(hasOffsetParams) {
-                x = res.location.value.x - (res.size.value.width / 2) + xoffset;
-                y = res.location.value.y - (res.size.value.height / 2) + yoffset;
+                x = res.location.value.x + xoffset;
+                y = res.location.value.y + yoffset;
             }
 
             return this.touchMove(x, y);