Fix #98: Use jnr-unixsocket instead of junixsocket.

A few notes :

- I've run the tests and noticed intermitent failure of testSsl from DefaultDockerClientTest, but this happens even before this change so it seems unrelated.
- commons-lang:commons-lang:2.4 was already an indirect dependency brought in by the unix-socket-factory artifact and it is in fact a build-time dependency for DefaultDockerClientTest so it should be listed.
- All of the classes marked unimplemented do not seem to be used by the underlying API currently.