Display date and version of the build.

[Kazuhisa Hara]

like this way.

$ docker version
Client:
 Version:         1.13.1
 API version:     1.26
 Package version: <unknown>
 Go version:      go1.8.3
 Git commit:      e98ceaa
 Built:           Thu Sep  7 18:08:36 2017
 OS/Arch:         linux/amd64

At a minimum, we need the compile date and golang version.
Now only display the software version.

$ ./docker-volume-sheepdog -version
Docker Volume Plugin for Sheepdog
Version : 0.0.1