Removing Trailing slash from parent url while building current resource url

Making sure Trailing slash is removed from parent url while building resource url in Path.base

This happened during building a resource using parent resource Url.
Failing example:

```javascript
var uri = '/api/parents/1/';
// with one(..) -> /api/parents/1//children/1
Restangular.oneUrl('parents', uri).one('children', 1).get();
// with all(..) -> /api/parents/1//children/
Restangular.oneUrl('parents', uri).all('children').getList();
```

There might be a better approach to handle such scenario, but i thought that a redundant slash doesn't look right anyway.

Regards,