Correction for Issue #20

- the options are not passed to the user type function:
w2fields.js, line 48

```javascript
-	w2field.customTypes[options.type.toLowerCase()].apply(this, arguments);
+	w2field.customTypes[options.type.toLowerCase()].call(this, options);
```

the arguments array is not interesting here as the object is already in this and it's important to have access to the field options.