Darken JSON strings in SnappyLight

JSON was so light as to be unusable by me so I darkened it by a couple shades.

Before: ![](http://f.cl.ly/items/2T342N1H3J3d421l0h2U/Q1fqJ_.png)

After: ![](http://f.cl.ly/items/3e0J1Z0M1p202K0H2A1U/G7z2v7.png)