Do not add trailing slash

- [x] Bug fix
- [x] Backwards compatible
- [x] Tests pass

```javascript
    Restangular.one('policy', '').get();
```

From 0.8.4 to 0.8.6 this piece of code went from making the HTTP request `http://localhost/policy` to `http://localhost/policy/`. This PR will ensure a trailing slash is not added to the end of requests automatically.