fix(Mobile): Don't preventDflt container touches

event.preventDefault() in uiGridRenderContainer touchmove handler was
preventing momentum scrolling from working on mobile devices. Removing
this call seems to have allowed more natural mobile scrolling. I have only
tested on Android as that's what's available but hopefully iOS will be
better as well

src/js/core/directives/ui-grid-render-container.js

@@ -175,8 +175,6 @@
                 event = event.originalEvent;
               }
 
-              event.preventDefault();
-
               var deltaX, deltaY, newX, newY;
               newX = event.targetTouches[0].screenX;
               newY = event.targetTouches[0].screenY;