Feature Request: Window Margins

[gilbertohasnofb]

Would it be possible to implement an option to set margin values? IMO having a small space between windows (just as few as 10 pixels) can really improve the overall look of the tiling. Apparently this is already implemented in the original project from which this is forked, e.g. see it mentioned here: https://github.com/vibou/vibou.gTile/issues/31