No warning is given when using implicit object names as arguments in template.

I use playframework 1.2.5, play-rythm 1.0-b8d, rythm 1.0-b9-20130519.121506-15

Controller:

```
renderArgs.put("lang", "My lang");
```

Template:

```
@args String lang;
```

Argument value is overriden, but silently. It would be nice to have a warning.
