Switch to built in rails server

Dockerfile

@@ -19,7 +19,6 @@ RUN cd /usr/bin && \
 # explicitly add Gemfile and install dependencies using bundler to make use of
 # Docker's caching
 WORKDIR /osem/
-RUN gem install puma
 COPY Gemfile /osem/
 COPY Gemfile.lock /osem/
 RUN bundle install --without test development

docker/init.sh

@@ -42,4 +42,4 @@ echo ">>> Precompiling assets..."
 bundle exec rake assets:precompile
 
 echo ">>> Starting application server..."
-exec puma -e production
+exec bundle exec rails server -e production -p 9292