update packages, use yarn , use node 8

Dockerfile

@@ -1,3 +1,14 @@
-FROM node:4-onbuild
 # replace this with your application's default port
+FROM node:8
+RUN mkdir -p /usr/src/app
+RUN curl -o- -L https://yarnpkg.com/install.sh | bash
+WORKDIR /usr/src/app
+
+ARG NODE_ENV
+ENV NODE_ENV $NODE_ENV
+COPY package.json /usr/src/app/
+RUN yarn install && yarn cache clean --force
+COPY . /usr/src/app
+
+CMD [ "yarn", "start" ]
 EXPOSE 7777