update terms aggs for 1.4.0; add children aggs

ES 1.4.0 includes additional fields for terms aggregations (e.g.
`sum_other_doc_count` -- see
http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-aggregations-bucket-terms-aggregation.html)
that have not been part of the Elastic response. We added those fields
now.

We also added the new children aggregation that has been included in
1.4.0.
add fuzzy search queries

We add `fuzzy`, `fuzzy_like_this` and `fuzzy_like_this_field` queries
and updated the README.