Git 1.6 support

`git-symbolic-ref` needs to be `git symbolic-ref`

git.zsh

@@ -11,7 +11,7 @@ ZSH_THEME_GIT_PROMPT_CLEAN=""
 
 # get the name of the branch we are on
 function git_prompt_info() {
-  ref=$(git-symbolic-ref HEAD 2> /dev/null) || return
+  ref=$(git symbolic-ref HEAD 2> /dev/null) || return
   echo "$ZSH_THEME_GIT_PROMPT_PREFIX${ref#refs/heads/}$(parse_git_dirty)$ZSH_THEME_GIT_PROMPT_SUFFIX"
 }