Add tree templates to hub

Ability to add files to the tree on each git init (ie: a default readme.md, a default .gitignore etc)

```

    # default template always gets copied in
    $ git init 
    > git init 
    > cp -r ~/.hubtemplate/. .
    
    # create a clean repo
    $ git init -c
    > git init

    # use a custom template directory
    $ git init -t template_dir
    > git init
    > cp -r template_dir/. .
	
```