add simple mrtazz theme based on robbyrussell

- simple theme
- hostname and current folder on left prompt
- git branch and working tree status on the right

themes/mrtazz.zsh-theme

+PROMPT='%{$fg_bold[red]%}%m%{$reset_color%}:%{$fg[cyan]%}%c%{$reset_color%}:%# '
+RPROMPT='%{$fg_bold[green]%}$(git_prompt_info)%{$reset_color%}% '
+
+ZSH_THEME_GIT_PROMPT_PREFIX="<%{$fg[red]%}"
+ZSH_THEME_GIT_PROMPT_SUFFIX="%{$reset_color%}"
+ZSH_THEME_GIT_PROMPT_DIRTY="%{$fg[green]%} %{$fg[yellow]%}✗%{$fg[green]%}>%{$reset_color%}"
+ZSH_THEME_GIT_PROMPT_CLEAN="%{$fg[green]%}>"