Ruby mogilefs-client 3.3.0

No changes since 3.3.0-rc1.

We now correctly timeout requests to slow trackers and avoid
reusing the socket after timeouts (as old responses can arrive
late).  A big thanks to David Rasch for helping with
timeout/idempotency issues for this release.

Minor documentation/packaging updates, it should be easier
to build a pre-release gem now (see HACKING doc).