Removing the middle man for AMD/CommonJS loaders

Removing the middle man for AMD/CommonJS loaders by storing a reference to `ZeroClipboard` as a DOM property of the ZeroClipboard-owned Flash object element.

Also added a bit of XSS hardening to the SWF by verifying that `ExternalInterface.objectID` matches the expected value. `ExternalInterface.objectID` will always be `null` when the SWF is linked to directly for XSS attacks.

Fixes #388.