Also it includes various minor features and bugfixes. Full list of changes:

* Add signal API to Container interface
* Update github.com/opecontainers/specs to 5b31bb2b7771e5074a4eb14eca432da1ca5182d6
* Don't set /proc/<PID>/setgroups to deny in Go1.5
* Add debug message when unable to execute criu
* Remove reference to nsinit
* Replace dind with smaller script
* integration: show criu logs in a error case
* tests: dump/restore a container with cgroups
* Simplify and fix os.MkdirAll() usage
* Change default state directory to /run/oci
* Add TESTFLAGS to Makefile targets
* Update README.md to correct comment about spec and user
* Only add network info if NEWNET is set
* Fix files not closed in mountinfo parsing function
* signal: Fix leak
* test: propagate the error to the caller
* Swap check for systemd booted to use go-systemd method
* Vendor github.com/coreos/go-systemd/util
* Use /proc/self/exe as default for InitPath
* Adapt code to go-systemd/dbus v3
* Update github.com/coreos/go-systemd/dbus to v3
* typo: tempory -> temporary
* bring the loopback interface up
* systemd integration with container runtime for supporting sd_notify protocol
* Remount /sys/fs/cgroup as RO if MS_RDONLY was passed in m.Flags
* Update maintainers guide
* Create symlinks for merged cgroups
* ct: give criu informations about cgroup mounts
* Fix subsystem path with abs parent
* avoid infinite loop with GCCGO