feature: add partial update ability.
usage like indexing:

                $params = array(
                    '_refresh_' => false,
                    'index'     => $update->indice,
                    'type'      => $update->type,
                );

                $es->update($update->document, $id, $params);
Merge branch 'develop_update' of https://github.com/1e1/elasticsearch into develop_update