implement cmd/version

cmd/version/main.go

@@ -0,0 +1,12 @@
+// Command version is a utility that prints the current godrone version and
+// exits.
+package main
+
+import (
+	"fmt"
+	"github.com/felixge/godrone"
+)
+
+func main() {
+	fmt.Println(godrone.Version)
+}

version.go

@@ -0,0 +1,3 @@
+package godrone
+
+const Version = "0.1"