Modernize and clean up string formatting code in new JSON highlighting.
Modernize and clean up string formatting code in new JSON highlighting.

tomstuart/pygments,tomstuart/pygments,tomstuart/pygments,tomstuart/pygments,tomstuart/pygments,tomstuart/pygments,tomstuart/pygments,tomstuart/pygments,tomstuart/pygments,tomstuart/pygments,tomstuart/pygments,tomstuart/pygments,tomstuart/pygments,tomstuart/pygments,tomstuart/pygments