Merge pull request #1 from wizard04wsu/drag-event-attributes

add `draggingFile` event attribute for drag & drop events

Because the drag data is protected for most drag events (see http://www.w3.org/TR/html5/editing.html#dndevents), we can't determine if a file is being dragged by simply checking the length of event.dataTransfer.files. Checking for "Files" in event.dataTransfer.types isn't reliable either; e.g., "Files" is included even if you're just dragging an image element.

The dragstart and dragend events are not fired when dragging a file (or files) into the browser window (because the source of the drag is essentially unknown). This fact is used to determine if it's a file being dragged.

- add custom `draggingFile` attribute to the event object for drag & drop events. This indicates if it is one or more files being dragged into the browser window.
- change test files to demonstrate this
allow namespace injection