possiblity to toggle background

Hi, would be cool the possibility to disable toggle background (just a condition around this block: https://github.com/aviatesk/Zen-plus/blob/master/styles/zen-plus.less#L5 ),

because with that is impossible to use plugins that draw stuff in the background (like https://github.com/ojack/atom-hydra)

Start with styles/zen-plus.less at the referenced block around line 5 and inspect how the background behavior is applied. Determine the existing configuration or condition pattern needed to let users disable it, then verify that background-drawing plugins such as Atom Hydra can work when it is disabled.

Written by the indexing model from the issue text.