Fix Iframe sticky click with IE11/Edge

[ibio]

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When using IE, Edge(13, 14 and 15), if this react-draggable is in an iframe, the draggable item gets 'stuck' on the mouse if the user attempts to drag it off iframe/screen.

To reproduce: 1 Make sure react-draggable is in an iframe 2 Open IE browser 3 Try to click/drag the draggable item out of the iframe 4 Release mouse click(outside of the iframe). Observe as the user now moves mouse around the screen, the draggable item follows as if it's stuck to the pointer.

[ibio]

@STRML I've added try catch to deal with cross-origin situation. Please have a look the latest change and let me know what you think. Thanks :)