RSS River issue with feedforall

Adding a test case for issue #33. Can not reproduce it.

```sh
curl -XGET http://ESServerIP:9200/_river/attacks/_meta?pretty=true
{
  "type": "rss",
  "rss": {
    "feeds": [
           {
        "name": "sample",
        "url": "http://www.feedforall.com/sample.xml",
        "update_rate": "15m"
      }
    ]
  }
}
```

Closes #33.
(cherry picked from commit 04a40be)