options: support legacy options

if we get a message like:

```js
var context = {
  providers: {
    'Salesforce': true
  },
  'Salesforce': {
    object: 'Lead',
    lookup: { email: 'peter@initech.com' } }
  }
};

msg = new Facade({ context: context });
```

options method doesn't work properly:
```js
msg.options('Salesforce'); // => {}
```

cc @calvinfo