Dockerfile: Update and streamline steps

Does effectively the same things as before,
but now in a simpler/faster way.

Some of the changes take inspiration from
@btyy77c's dockerAlpine branch:
https://github.com/btyy77c/refugerestrooms/blob/dockerAlpine/Dockerfile

The PhantomJS install is based on (mostly copy-pasted from)
@nkovacs' phantomjs image from Docker Hub:
https://github.com/nkovacs/selenium-standalone-phantomjs/blob/c5f6bba218472270/Dockerfile#L19-L22

Dockerfile

@@ -1,38 +1,43 @@
 FROM ruby:2.5.3-slim
-ENV PHANTOM_JS=2.1.1
 
 # Add basic binaries
 RUN apt-get update \
-  && apt-get install -y bzip2 curl gnupg wget
-
-# Add the apt repository for yarn
-RUN curl -sS http://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add - && \
-  echo "deb http://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list
-
-# Add the apt-repository for the latest node.js
-RUN curl -sL https://deb.nodesource.com/setup_8.x | bash -
-
-RUN apt-get update -qq && apt-get install -y build-essential libpq-dev nodejs
-RUN apt-get install build-essential chrpath libssl-dev libxft-dev -y && \
-  apt-get install libfreetype6 libfreetype6-dev -y && \
-  apt-get install libfontconfig1 libfontconfig1-dev -y && \
-  cd ~ && \
-  export PHANTOM_JS="phantomjs-2.1.1-linux-x86_64" && \
-  wget https://github.com/Medium/phantomjs/releases/download/v2.1.1/$PHANTOM_JS.tar.bz2 && \
-  tar xvjf $PHANTOM_JS.tar.bz2 && \
-  mv $PHANTOM_JS /usr/local/share && \
-  ln -sf /usr/local/share/$PHANTOM_JS/bin/phantomjs /usr/local/bin && \
-  apt-get install -y yarn
-
-# Clean up the apt cache
-RUN rm -rf /var/lib/apt/lists/*
-
+  && apt-get install -y curl g++ gcc libfontconfig libpq-dev make patch xz-utils \
+  # Clean up the apt cache
+  && rm -rf /var/lib/apt/lists/*
+
+# Download, extract and install PhantomJS from archive hosted at bitbucket
+RUN curl -L https://bitbucket.org/ariya/phantomjs/downloads/phantomjs-2.1.1-linux-x86_64.tar.bz2 -O \
+  # Extract and clean up the PhantomJS archive
+  && tar xf phantomjs-2.1.1-linux-x86_64.tar.bz2 && rm phantomjs-2.1.1-linux-x86_64.tar.bz2 \
+  # Install PhantomJS binary to /usr/local/bin
+  && mv phantomjs-2.1.1-linux-x86_64/bin/phantomjs /usr/local/bin \
+  # Clean up extra (un-needed) PhantomJS files
+  && rm -rf phantomjs-2.1.1-linux-x86_64/
+
+# Specify a version of Node.js to download and install
+ENV NODEJS_VERSION=v10.15.3
+
+# Download and extract Node.js from archive supplied by nodejs.org
+RUN curl -L https://nodejs.org/dist/$NODEJS_VERSION/node-$NODEJS_VERSION-linux-x64.tar.xz -o nodejs.tar.xz \
+  && tar xf nodejs.tar.xz \
+  # Clean up the Node.js archive
+  && rm nodejs.tar.xz
+
+# Add Node.js binaries to PATH (includes Node and NPM, will include Yarn)
+ENV PATH="/node-$NODEJS_VERSION-linux-x64/bin/:${PATH}"
+
+# Install Yarn
+RUN npm install -g yarn
+
+# Make the "/refugerestrooms" folder, run all subsequent commands in that folder
 RUN mkdir /refugerestrooms
 WORKDIR /refugerestrooms
 
-COPY Gemfile /refugerestrooms/Gemfile
-COPY Gemfile.lock /refugerestrooms/Gemfile.lock
+# Install Ruby gems with Bundler
+COPY Gemfile Gemfile.lock /refugerestrooms/
 RUN bundle install
 
+# Install Node.js packages with Yarn
 COPY package.json yarn.lock /refugerestrooms/
-RUN yarn --pure-lockfile
+RUN yarn install --pure-lockfile