Extend Window with DataView

Adds [`DataView`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView) to Zombie's window scope. `DataView` is used in [browserify](https://github.com/substack/node-browserify), for example. I grab the constructor from the global scope when the window is created.

Let me know if there's anything I need to add or change to meet requirements.