Adding support for window.parent

In a browser, window.parent always === window at the topmost window. In
the case of Ejecta, since there will never be subwindows or frames, setting
window.parent to window is good enough.

For more information:

https://developer.mozilla.org/en-US/docs/Web/API/window.parent
Merge pull request #192 from amadeus/fix-window-top

Adding support for window.parent