Fix a bug which caused creation of empty images (and volumes) to crash. FIxes #995.
- Runtime: add regression test for issue #995
Merge pull request #996 from dotcloud/995-volumes-crash

- Runtime: fix a bug which caused creation of empty images (and volumes) to crash.
Bump version to 0.4.6
Merge pull request #997 from dotcloud/bump_0.4.6

Bump version to 0.4.6
Fixing hack/Vagrantfile to use uname for aufs linux extras

Conflicts: hack/Vagrantfile
Resolved by: Daniel Mizyrycki <daniel@dotcloud.com>
Merge pull request #998 from dotcloud/861-hack-vagrant

Fixing hack/Vagrantfile to use uname for aufs linux extras