Add --org flag to bash completion for git fork

Because this is an array of flags now, adding new flags is as simple as
adding more elements to the array and to the case statement.

etc/hub.bash_completion.sh

@@ -218,13 +218,13 @@ EOF
     esac
   }
 
-  # hub fork [--no-remote] [--remote-name]
+  # hub fork [--no-remote] [--remote-name] [--org]
   _git_fork() {
-    local i c=2 flags="--no-remote --remote-name"
+    local i c=2 flags="--no-remote --remote-name --org"
     while [ $c -lt $cword ]; do
       i="${words[c]}"
       case "$i" in
-        --no-remote|--remote-name)
+        --no-remote|--remote-name|--org)
           flags=${flags/$i/}
           ;;
       esac