Add my (cypher's) zsh prompt

Based on Evan's prompt, it uses colors, shows the exit status of the
last command if it was non-zero, and displays "#" when running
with elevated privileges

themes/cypher.zsh-theme

+# Based on evan's prompt
+# Shows the exit status of the last command if non-zero
+# Uses "#" instead of "»" when running with elevated privileges
+PROMPT="%m %B%F{red}::%b %B%F{green}%3~%(0?. . %F{red}%? )%F{red}%(0!.#.»)%b%F{white} "