Add version command

[kars7e]

$ make cli-darwin
GOOS=darwin go build -ldflags " -X github.com/vmware/dispatch/pkg/version.version=v0.1.7 -X github.com/vmware/dispatch/pkg/version.buildDate=2018-03-08T02:23:12Z -X github.com/vmware/dispatch/pkg/version.commit=7a5a611a74190d7b84ef1da3767ce58d2ad693bd " -o bin/dispatch-darwin ./cmd/dispatch

$ bin/dispatch-darwin version
v0.1.7-7a5a611a74

Release pipeline would need some tunning to automatically bump versions

[berndtj]

I realize this is late... I think we can enhance this to include client and server versioning and also get the version from the build rather than having to remember to bump the version in the makefile.

[berndtj]

We're going to forget to do this. I'd like a future version of this change to pull the version from a file which effectively is written by the build system.

[berndtj]

How can we get the server version?