zdb_significant_terms()to work for such fields. Note that if you want that ability, you'll need to
REINDEXany existing ZomboDB indexes.
zdb_tally()is now honored
ZomboDB v2.1.38 now only supports Elasticsearch v1.7.1 or later. This is a reaction to Elasticsearch Issue 12487 which was not fixed in the 1.5 branch. Trying to support multiple versions of Elasticsearch is a bit of a losing proposition because they don't guarantee plugin API (source or binary) between major versions.
As such, you'll need to (and should!) upgrade your ES cluster to 1.7.1. You should follow the Elasticsearch instructions for upgrading, but make sure to set the configuration keys that ZomboDB requires.
Thanks to @johnrballard and @ryancutter for their contributions!