Update to Lucene 6.4.0
Update to Lucene 6.4.0

Closes #303.

dadoonet/fscrawler,dadoonet/fsriver,kneubi/fscrawler,dadoonet/fscrawler,dadoonet/fsriver,kneubi/fscrawler,dadoonet/fscrawler,dadoonet/fsriver,kneubi/fscrawler