cadaver complain about missing Lock-Token header field

with DAV4Rack 0.2.10 in a Rails 3.2 app

``` bash
dav:/webad> lock foo.txt
```

in lib/dav4rack/controller.rb (ligne 239),  add :

``` ruby
response['Lock-Token'] = locktoken 
```

and it work's but don't  konw if it's valid or not.
