Tests on Travis fixed.

On Travis, [tests](https://travis-ci.org/clojurewerkz/elastisch/jobs/10863208) fail due to the `ES_CLUSTER_NAME` env var which is not set. They still don’t pass (there’s a `java.lang.IllegalArgumentException: Unable to resolve classname: double, compiling:(clojurewerkz/elastisch/native/conversion.clj:507)` with `dev,1.3` profile), but that’s a “normal failure”, i.e. due to the code, not a problem in the test suite.