Upgrade for ES0.90.4

Hi,

thanks for this plugin! I need to use it against ES 0.90.4 so I've made 2 changes:
Firstly removed the splitIndices/splitTypes methods as they are removed by this commit:
https://github.com/elasticsearch/elasticsearch/issues/3680

Also, the org.elasticsearch.common.collect.Sets type utilities seem to have been removed, so I've just replaced these with new HashSet etc.

Please let me know if this is ok.