Upgrade to elasticsearch 1.4.1

This pull request contains everything to upgrade to 1.4.1. Please feel free to adopt it into master or create a new 1.4.1 branch.

Kind regards,
Milo van der Linden
This was intendedly added to separate unit tests and integration tests (see executions below). You can run them using:
```bash
mvn clean test
mvn clean integration-test
mvn clean test integration-test
mvn clean verify # similar to the previous one
```