fix(ionList): make reorder follow an offset list as it scrolls

Author: ajoslin

Diff for: js/views/listView.js

@@ -193,7 +193,7 @@
   ReorderDrag.prototype._moveElement = function(e) {
     var y = e.gesture.center.pageY -
       this._currentDrag.elementHeight + 
-      this._currentDrag.scrollDelta - 
+      this.scrollView.getValues().top -
       this.listEl.offsetTop;
     this.el.style[ionic.CSS.TRANSFORM] = 'translate3d(0, '+y+'px, 0)';
   };
@@ -215,8 +215,7 @@
       startIndex: startIndex,
       placeholder: placeholder,
       scrollHeight: scroll,
-      list: placeholder.parentNode,
-      scrollDelta: 0
+      list: placeholder.parentNode
     };
 
     this._moveElement(e);
@@ -243,12 +242,10 @@
 
       if (e.gesture.deltaY < 0 && pixelsPastTop > 0 && scrollY > 0) {
         this.scrollView.scrollBy(null, -pixelsPastTop);
-        this._currentDrag.scrollDelta -= pixelsPastTop;
       }
       if (e.gesture.deltaY > 0 && pixelsPastBottom > 0) {
         if (scrollY < this.scrollView.getScrollMax().top) {
           this.scrollView.scrollBy(null, pixelsPastBottom);
-          this._currentDrag.scrollDelta += pixelsPastBottom;
         }
       }
     }