Margins / gaps

[torrance]

Just a feature request: to integrate the ability to specify margins around the screen and gaps between windows.

eg. the sort of functionality provided by the i3-gaps project: https://github.com/Airblader/i3

[polyjitter]

This omission is the reason I have not been really using slinger. If gaps and margins could be set I'd be much more willing to use it over shellshape