Blend using queries

Previously, blends were adding elevated posts to the desired index, but this was not the best way to do it.  Now, the query files allow for passing in ElasticSearch filters so the blend can be handled at the query level.

Your query files should now follow this convention:

```
{
  "name": "Verbose Name",
  "query": {
    "size": 10,
    "sort": "date:desc"
  },
  "filters": [
    {
      "example": "filter"
    }
  ]
}
```

Also, the Query methods search() and search_with_url_arguments() have been combined into one method due to the amount of overlapping code.  Tests were updated as well.