Add support for search template's

[cmodijk]

It would me cool to support te Template query and be able to store search templates.

http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-template.html http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/query-dsl-template-query.html

[ruflin]

Nice feature. You could already use it through the raw query (http://elastica.io/example/raw-array-query.html) but I agree we should have it as a native feature implemented. Can you open a pull request with a suggested implementation?