Move version printing to version package

Signed-off-by: Stephen J Day <stephen.day@docker.com>

version/print.go

@@ -0,0 +1,26 @@
+package version
+
+import (
+	"fmt"
+	"io"
+	"os"
+)
+
+// FprintVersion outputs the version string to the writer, in the following
+// format, followed by a newline:
+//
+// 	<cmd> <project> <version>
+//
+// For example, a binary "registry" built from github.com/docker/distribution
+// with version "v2.0" would print the following:
+//
+// 	registry github.com/docker/distribution v2.0
+//
+func FprintVersion(w io.Writer) {
+	fmt.Fprintln(w, os.Args[0], Package, Version)
+}
+
+// PrintVersion outputs the version information, from Fprint, to stdout.
+func PrintVersion() {
+	FprintVersion(os.Stdout)
+}