Enable eventM

Hi, I have been using `eventM` using [`tryEvent`](http://hackage.haskell.org/packages/archive/gtk/0.12.4/doc/html/Graphics-UI-Gtk-Gdk-EventM.html#t:EventM) as follows.

```haskell
network <- compile $ do
    eDeleted <- eventM window deleteEvent $ tryEvent $ liftIO mainQuit
actuate network
```
Is this the correct way to do this or did you have something else in mind? Depending on that, please accept or reject this change.