patch to bira.zsh-theme in oh my zsh

zsh-bira-theme.diff

diff --git a/themes/bira.zsh-theme b/themes/bira.zsh-theme
index 2157204..003cb92 100644
--- a/themes/bira.zsh-theme
+++ b/themes/bira.zsh-theme
@@ -4,7 +4,7 @@ local return_code="%(?..%{$fg[red]%}%? ↵%{$reset_color%})"
 local user_host='%{$terminfo[bold]$fg[green]%}%n@%m%{$reset_color%}'
 local current_dir='%{$terminfo[bold]$fg[blue]%} %~%{$reset_color%}'
 local rvm_ruby=''
-if which rvm-prompt &> /dev/null; then
+if [ -e ~/.rvm/bin/rvm-prompt ]; then
   rvm_ruby='%{$fg[red]%}‹$(rvm-prompt i v g)›%{$reset_color%}'
 else
   if which rbenv &> /dev/null; then