[git] checking for existence of hub

if hub is present, alias git to hub

hub can be installed on os x using homebrew - `brew install hub`

https://github.com/defunkt/hub

git/git.zsh

@@ -20,3 +20,7 @@ function git_rename() {
     git mv $1 "${2}-"
     git mv "${2}-" $2
 }
+
+if which hub &> /dev/null; then
+    alias git='hub'
+fi