pass options to route_for_task

Passed options can be used in lookup_route too. e.g. I'm trying to implement priority queue support like this:

Passing `priority=True` to `send_task`:
`celery.execute.send_task('support.test', priority=True)`

Then route requests using a custom Router:

```
class MyRouter(object):
    def route_for_task(self, task, args=None, kwargs=None, options=None):
        if options and options['priority']:
            return {'queue': task + ".priority"}
        return {'queue': task}
```