Fix preprompt formatting in zsh precmd.

The format is now "%s" to prevent any percents in the preprompt
from being interpreted as a printf format.
Move the coloring inside the if to avoid emitting redundant escape sequences.
Tiny formatting fixes.
Merge branch 'master' of github.com:mikelward/conf

Conflicts:
	env
	zshrc
Fix zshrc -> shrc symlink after merge.