Uses separate AppIconMenu forked from 3.12 and 3.10, for each shell version respectively

Fixes #20 ?
The original popover uses AppIconMenu which defaults the PopupMenu to appear on right side (or left side if you're RTL) by calling it's parent initialization (which is PopupMenu)
`this.parent(source.actor, 0.5, side);`
I need to change the `side` to `St.Side.TOP`. If I could only  easily extends the original AppIconMenu and change it, but can't. Extending original AppIconMenu means if I call `this.parent()` it means that I call AppIconMenu initialization, which has no `side` option. Therefore, I choose to fork AppIconMenu from 3.12, which will give a problem in 3.10.

Picture below is a screenshot of implemented popover versus the original one. The implemented one has more options that **should not be available** in 3.10, but clicking those items has no effect whatsoever.
![screenshot from 2014-04-16 05 20 38](https://cloud.githubusercontent.com/assets/749098/2713890/f663b6a2-c4ed-11e3-8d09-f6e0dad7ba92.png)
![screenshot from 2014-04-16 06 31 42](https://cloud.githubusercontent.com/assets/749098/2713889/f66363fa-c4ed-11e3-82de-403575bc4894.png)

I need all of your suggestion, should we use the AppIconMenu forked from 3.12 or the original 3.10? And should we choose only one version to develop in?