Convoy v0.5.0-rc1 release

WARNING: From v0.5.0 forward, we won't support configuration file PRIOR to v0.5.0. It's suggested to backup your old configuration directory(normally /var/lib/convoy), rename it and back it up, and start a new Convoy v0.5.0 daemon with a new /var/lib/convoy. You can use Convoy backup/restore feature to restore previous volumes, e.g. back it up in the old Convoy version, then restore it in the new version.

This is a big update.

1. We've updated internal configuration file structure, to get rid of global level locks, and remove quite some complexity. But this result in broken backward compatibility. Please don't run v0.5.0 with old Convoy root.
2. Support Docker v1.10+. We've updated our API to latest Docker Volume Plugin spec, implemented Get/List method.
3. Thanks to @jinuxstyle , now we supports XFS as alternative file system(#106), as well as start daemon ignore current configuration file(#120) and support delete multiple volumes(#100).

Please report any issue you found. Thanks and enjoy!