Improve Dockerfile, and added alpine version

.dockerignore

@@ -0,0 +1,7 @@
+.git
+test
+Dockerfile*
+.gitignore
+.dockerignore
+.travis.yml
+*.md

Dockerfile

@@ -1,17 +1,22 @@
-
 FROM ruby:2.4.1
-MAINTAINER Conor Heine <conor.heine@gmail.com>
-
-RUN apt-get update
-RUN apt-get -y install git nodejs
-COPY . /devdocs
-RUN gem install bundler
 
 WORKDIR /devdocs
 
-RUN bundle install --system
-RUN thor docs:download --all
+RUN apt-get update && \
+    apt-get -y install git nodejs && \
+    gem install bundler && \
+    rm -rf /var/lib/apt/lists/*
+
+COPY Gemfile Gemfile.lock Rakefile /devdocs/
+
+RUN bundle install --system && \
+    rm -rf ~/.gem /root/.bundle/cache /usr/local/bundle/cache
+
+COPY . /devdocs
+
+RUN thor docs:download --all && \
+    thor assets:compile && \
+    rm -rf /tmp
 
 EXPOSE 9292
 CMD rackup -o 0.0.0.0
-

Dockerfile-alpine

@@ -0,0 +1,17 @@
+FROM ruby:2.4.1-alpine
+
+WORKDIR /devdocs
+
+COPY . /devdocs
+
+RUN apk --update add nodejs build-base libstdc++ gzip git zlib-dev && \
+    gem install bundler && \
+    bundle install --system --without test && \
+    thor docs:download --all && \
+    thor assets:compile && \
+    apk del gzip build-base git zlib-dev && \
+    rm -rf /var/cache/apk/* /tmp ~/.gem /root/.bundle/cache \
+    /usr/local/bundle/cache /usr/lib/node_modules
+
+EXPOSE 9292
+CMD rackup -o 0.0.0.0