update installation docs.
update installation docs.

tomstuart/pygments,tomstuart/pygments,spencerlyon2/pygments,spencerlyon2/pygments,tomstuart/pygments,tomstuart/pygments,spencerlyon2/pygments,spencerlyon2/pygments,tomstuart/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,tomstuart/pygments,tomstuart/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,spencerlyon2/pygments,tomstuart/pygments,tomstuart/pygments,tomstuart/pygments,tomstuart/pygments,spencerlyon2/pygments,tomstuart/pygments,spencerlyon2/pygments,tomstuart/pygments,tomstuart/pygments,tomstuart/pygments,spencerlyon2/pygments