This will generate the version based on git tags. So if it is built
directly on a tag it will use the tag name and if it is built off a
commit that isn't a tag it will look like:
$ curl localhost:7001
0-267-ga39cf1c
add a simple build script that sets up a gopath and uses the current git
directory for the github.com/coreos/etcd packages.
There aren't a lot of great alternatives to doing it this way unless we
want to check in all of the dependencies into the repo (which is
actually a good practice probably).
