update to latest version of Node.js for 10.x (#202)

diff --git a/Dockerfile b/Dockerfile
index 8819e09..cc700f9 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM node:10.15.2
+FROM node:10.15.3
 
 # only package.json
 ADD package.json /