Add podman version

Copy the way cri-o does this by adding a libpod/version
Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

Closes: #343
Approved by: mheon

cmd/podman/main.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/containers/storage/pkg/reexec"
 	"github.com/pkg/errors"
+	"github.com/projectatomic/libpod/version"
 	"github.com/sirupsen/logrus"
 	"github.com/urfave/cli"
 )
@@ -14,8 +15,7 @@ import (
 // This is populated by the Makefile from the VERSION file
 // in the repository
 var (
-	podmanVersion = ""
-	exitCode      = 125
+	exitCode = 125
 )
 
 func main() {
@@ -30,11 +30,7 @@ func main() {
 	app.Name = "podman"
 	app.Usage = "manage pods and images"
 
-	var v string
-	if podmanVersion != "" {
-		v = podmanVersion
-	}
-	app.Version = v
+	app.Version = version.Version
 
 	app.Commands = []cli.Command{
 		attachCommand,

version/version.go

@@ -0,0 +1,4 @@
+package version
+
+// Version is the version of the build.
+const Version = "0.3-dev"