A new tutorial on how to integrate with Gtk

[Lalaland]

We do not have a tutorial on how to integrate with Gtk(we already have wxWidgets and Qt, the other major two gui frameworks), so I have created a guide based off Shy Guy's work.
I think we should add this next to the other tutorials.

I downloaded the Qt guide html page and changed the contents.
The guide can be found here: http://lalaland.github.com/gtkGuide.html

Hope you find it useful!

[Laurent]

Good work, thanks