jQuery-dependent simulated drag workaround

Anyone interested in this? Using the method that [Dave Haeffner outlines](http://elementalselenium.com/tips/39-drag-and-drop), we can get drag working again for HTML5 pages. 

downsides:

* hard dependency on jQuery either being on the page or manually loaded in webdriver
* dragging is not actually in the JSONWireProtocol
* We'd have to include a js file in this perl module (where to put it?)
* doesn't seem to always work, may depend on the drag implementation of the actual page under test
* The "preferred" implementation used by other bindings is ActionChains, and when the webdriver bug is fixed, we'll need to deprecate this again
* The previous implementation of drag wanted pixel coordinates, and we're changing that API to want a WebElement (this is ... not really a huge deal, as the previous implementation was completely busted).

upsides:

* we could actually drag something. I tried out a python ActionChains example and it failed as expected due to the [aforementioned webdriver bug](https://code.google.com/p/selenium/issues/detail?id=6315), so even the "preferred" actionchains method doesn't work.