Dockerfile

FROM ruby:2.2.2
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev

# for a JS runtime                                                    
RUN apt-get install -y nodejs                                         

RUN mkdir /app                                                        
WORKDIR /app                                                          
ADD Gemfile /app/Gemfile                                              
RUN bundle install
ADD . /app

FROM ruby:2.2.2
WORKDIR /app                                                          

RUN apt-get update -qq && apt-get install -y build-essential libpq-dev

# for a JS runtime                                                    
RUN apt-get install -y nodejs                                         

ADD Gemfile /app/Gemfile                                              
RUN bundle install

ADD . /app```

FROM ruby:2.2.2
WORKDIR /app                                                          

RUN \
  apt-get update -qq && \
  apt-get install -y build-essential libpq-dev nodejs && \
  apt-get clean && \
  rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*

ADD Gemfile /app/Gemfile                                              
RUN bundle install

ADD . /app```