Repeat response n times

You are able to specify the number of times to repeat the same response.

```js
nock('http://zombo.com').get('/').times(2).reply(200, 'Ok');

http.get('http://zombo.com/'); // respond body "Ok"
http.get('http://zombo.com/'); // respond body "Ok"
http.get('http://zombo.com/'); // respond with zombo.com result
```