Make HDFS to ES indexing tests self-containd and add them to CI

- Upload test data to a local in-memory Hadoop MiniDFSCluster
- Index test data in a local in-memory elasticsearch node
- Update config files (JUnit, Maven, and Travis setup)
Merge pull request #43 from fsteeg/tests

Make HDFS to ES indexing tests self-containd and add them to CI