[sheepdog] stable branch release: v0.6.1

[Hitoshi Mitake]

Hi sheepdog users and developers,

I released stable-v0.6.1. You can download a source archive from this
URL:
https://github.com/collie/sheepdog/releases/tag/stable-v0.6.1

You can also use a newly created tag stable-v0.6.1 for obtaining the
source tree.

This release consists bug fixes for major known problems and
improvements for packaging. Especially the stability of object cache
is improved compared to v0.6.0. If your sheepdog deployment is turning
on object cache, updating will be helpful.

Thanks,
Hitoshi