Use Node 8 in Docker.

docker/node/Dockerfile

@@ -1,17 +1,21 @@
-FROM node:6.14-alpine
+FROM node:8-alpine
 
 RUN apk update \
     && apk add --no-cache git
 
 RUN set -ex \
   && apk add --no-cache --virtual .build-deps ca-certificates openssl bzip2 \
-  && wget -qO- "https://github.com/dustinblackman/phantomized/releases/download/2.1.1/dockerized-phantomjs.tar.gz" | tar xz -C / \
-  && npm install -g phantomjs \
+  && wget -qO- "https://github.com/dustinblackman/phantomized/releases/download/2.1.1a/dockerized-phantomjs.tar.gz" | tar xz -C / \
+  && npm config set user 0 \
+  && npm install -g phantomjs-prebuilt \
   && apk del .build-deps
 
+ENV PHANTOMJS_BIN /usr/local/bin/phantomjs
+
 WORKDIR /srv/app
 
 COPY package.json /srv/app
+COPY package-lock.json /srv/app
 
 RUN npm install