Add support to :params for custom_filters_score

Just added support to use `params` with `custom_filters_score`. Params are often necessary when creating more complex score scripts. For example:

```ruby
query do
  custom_filters_score do
    query { string 'volmer' }
          
    params now: Time.now.to_i * 1000
          
    filter do
      filter 'exists', field: 'created_at'
      script "((0.08 / ((3.16*pow(10,-11)) * abs(now - doc['created_at'].date.getMillis()) + 0.05)))"
    end
  end
end
```
Thanks to [@thor27](https://github.com/thor27) and [Jon Tai's blog post](http://jontai.me/blog/2013/01/advanced-scoring-in-elasticsearch/).