Allow adding options without a method

By allowing options without a method we can add options to a sub set of
routes:

```javascript
Aviator.setRoutes({
  '/users': {
    target:     usersTarget,
    '/*':       { options: { bartyMcFly: true },
    '/:uuid':   'show',
    '/recent':  'listRecent'
  }
});
```
Merge pull request #15 from swipely/allow_options_with_no_method

Allow adding options without a method