In robbyrussell, when last status is 0, the prompt should be green, otherwise...

In robbyrussell, when last status is 0, the prompt should be green, otherwise it should be red, just like oh-my-zsh

themes/robbyrussell/README.md

 ## robbyrussell
 The default theme – cloned from oh-my-zsh.
 
-![robbyrussell theme](http://f.cl.ly/items/2q0v3i3y2E1F0C1R3C1y/Screen%20Shot%202013-08-06%20at%2017.52.17%20.png)
+![robbyrussell theme](https://bachue.github.io/oh-my-fish/images/robbyrussell-screenshot.png)
 
 
 #### Characteristics
 
 * Displays git information in the command prompt when available.
+* If the last command was failed, the indicator would be red, otherwise it's green

themes/robbyrussell/fish_prompt.fish

@@ -8,13 +8,19 @@ function _is_git_dirty
 end
 
 function fish_prompt
+  set -l last_status $status
   set -l cyan (set_color -o cyan)
   set -l yellow (set_color -o yellow)
   set -l red (set_color -o red)
   set -l blue (set_color -o blue)
+  set -l green (set_color -o green)
   set -l normal (set_color normal)
 
-  set -l arrow "$red➜ "
+  if test $last_status = 0
+      set arrow "$green➜ "
+  else
+      set arrow "$red➜ "
+  end
   set -l cwd $cyan(basename (prompt_pwd))
 
   if [ (_git_branch_name) ]