ENH: Add etc/.i3/Makefile with help, help_i3, test, and status (make help_i3)
DOC,CLN: etc/.i3/config: Add requirements section and update shortcut comments
ENH: etc/.i3/config: add  (feh, ~/wallpaper.png)
ENH: etc/.i3/config: add <alt><Backspace> to toggle floating window (scratchpad)
BUG: etc/.i3/config: exit fullscreen for popups (e.g. '10s to screensaver')