Update Dockerfile, install Chrome and Chromedriver

as wraith now supports headless chrome, it can be installed in the
docker container - also update nodejs to version 8 and use the ruby
version specified by the repository's .ruby-version file

Dockerfile

@@ -1,16 +1,40 @@
-FROM ruby:2.1.2
+FROM ruby:2.4.1
 
-# some of ruby's build scripts are written in ruby
-# we purge this later to make sure our final image uses what we just built
-RUN apt-get update
-RUN echo "export phantomjs=/usr/bin/phantomjs" > .bashrc
-RUN apt-get install -y libfreetype6 libfontconfig1 nodejs npm libnss3-dev libgconf-2-4
-RUN ln -s /usr/bin/nodejs /usr/bin/node
-RUN npm install npm
-RUN npm install -g phantomjs@2.1.7 casperjs@1.1.1
+WORKDIR /wraith
+
+RUN curl -sL https://deb.nodesource.com/setup_8.x | bash -
+RUN apt-get install -y libfreetype6 libfontconfig1 nodejs libnss3-dev libgconf-2-4 \
+	&& rm -rf /var/lib/apt/lists/*
+
+# make sure npm does not need sudo: https://docs.npmjs.com/getting-started/fixing-npm-permissions
+RUN mkdir /wraith/.npm-global
+ENV NPM_CONFIG_PREFIX=/wraith/.npm-global
+ENV PATH=/wraith/.npm-global/bin:$PATH
+
+# install with --unsafe-perm because of https://github.com/Medium/phantomjs/issues/707
+RUN npm install -g phantomjs-prebuilt casperjs --unsafe-perm
 RUN gem install wraith --no-rdoc --no-ri
 RUN gem install aws-sdk --no-rdoc --no-ri
 
+# install chrome and chromedriver (unzip is needed for installing chromedriver)
+RUN wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | apt-key add - \
+    && echo "deb http://dl.google.com/linux/chrome/deb/ stable main" > /etc/apt/sources.list.d/google.list \
+    && apt-get update \
+    && apt-get install -y google-chrome-stable unzip \
+    && rm -rf /var/lib/apt/lists/* \
+    && sed -i 's|HERE/chrome"|HERE/chrome" --disable-setuid-sandbox --no-sandbox|g' \
+           "/opt/google/chrome/google-chrome" \
+    && google-chrome --version
+
+RUN export CHROMEDRIVER_RELEASE=$(curl --location --fail --retry 3 http://chromedriver.storage.googleapis.com/LATEST_RELEASE) \
+    && curl --silent --show-error --location --fail --retry 3 --output /tmp/chromedriver_linux64.zip "http://chromedriver.storage.googleapis.com/$CHROMEDRIVER_RELEASE/chromedriver_linux64.zip" \
+    && cd /tmp \
+    && unzip chromedriver_linux64.zip \
+    && rm -rf chromedriver_linux64.zip \
+    && mv chromedriver /usr/local/bin/chromedriver \
+    && chmod +x /usr/local/bin/chromedriver \
+    && chromedriver --version
+
 # Make sure decent fonts are installed. Thanks to http://www.dailylinuxnews.com/blog/2014/09/things-to-do-after-installing-debian-jessie/
 RUN echo "deb http://ftp.us.debian.org/debian jessie main contrib non-free" | tee -a /etc/apt/sources.list
 RUN echo "deb http://security.debian.org/ jessie/updates contrib non-free" | tee -a /etc/apt/sources.list