Search upwards for a draggable element in touchstartDelay
Search upwards for a draggable element in touchstartDelay

#75 added a very useful ability to delay dragging, but it only works if the direct target of the first touch is itself draggable. This patch adds a search up the tree for a draggable element, just like how `touchstart` does. This makes dragging work on my project :-).
xStrom/ios-html5-drag-drop-shim,xStrom/ios-html5-drag-drop-shim,timruffles/ios-html5-drag-drop-shim,timruffles/ios-html5-drag-drop-shim