removed None path tests
jpype backend changed to raise ValueError on an empty path
jpype backend: fixed hdfs file write
jpype backend: {p,}read_chunk changed to support bytearrays
jpype backend: chown changed to a no-op if user & group are null
jpype backend: changed get_capacity to raise RuntimeError on a local fs
jpype backend: changed get_hosts to raise ValueError on negative start/length
Merge pull request #23 from simleo/fix_jpype_backend_21

Fix jpype backend