Re: Documentation colour theme

[flyx]

Another opinion on text color from 
[here](http://forum.nim-lang.org///practicaltypography.com/color.html):

> But con­sider mak­ing body text on screen dark gray rather than black. 
> Screens have more se­vere con­trast than pa­per, and thus are more tir­ing to 
> read at full con­trast. This is be­cause screens pro­duce color by emit­ting 
> light di­rectly, whereas pa­per pro­duces color by ab­sorb­ing and 
> re­flect­ing am­bi­ent light.

I would also prefer text color to be a bit darker. But black is overkill.