(#5714) - Switch window.close to brackets.app.quit

Quitting brackets using alt + f4 or the close button at top right corner does not close the program with the first try. Although, it will close after the second time.

Using file -> Quit will quit brackets as expected.
I am using Kubuntu 12.04.

Changing window.close() to brackets.app.quit() seemed to fix the problem and not to break anything in the process.