Add content type to version response

@@ -52,6 +52,7 @@ func (handler *ApiHandler) ServeHTTP(
 	dirs := strings.Split(request.URL.Path, "/")
 	switch dirs[0] {
 	case "version":
+		response.Header().Set("Content-Type", "application/json")
 		v, err := version.Versions.Json()
 		if err != nil {
 			http.Error(response, "Unable to encode version information", 500)