update node.js version to 10.16.3 (#215)

diff --git a/Dockerfile b/Dockerfile
index deadc15..f20e7a1 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -15,7 +15,7 @@
 # limitations under the License.
 #
 
-FROM node:10.16.0
+FROM node:10.16.3
 
 # only package.json
 ADD package.json /