Remove Docker

I don't use or support Docker for Keep a Changelog development.

I recommend using rbenv or chruby to develop with Ruby. Docker is way too much
overhead (and power usage) on macOS to run something as simple as a middleman site.
# Title

# Tell me everything!

# Co-authors (they will be credited on GitHub as well)
# Co-authored-by: Carolina Powers <carolinapoloni@gmail.com>
# Co-authored-by: Meg Kline-Tuls <meglktuls@gmail.com>
# Co-authored-by: Will <will-soto@pluralsight.com>
# Co-authored-by: thatchej <jaron-thatcher@pluralsight.com>

Dockerfile

@@ -1,20 +0,0 @@
-FROM ruby:2.3-alpine
-
-RUN apk add --update \
-  build-base \
-  libxml2-dev \
-  libxslt-dev \
-  nodejs
-
-# throw errors if Gemfile has been modified since Gemfile.lock
-RUN bundle config --global frozen 1
-
-WORKDIR /usr/src/app
-
-COPY Gemfile Gemfile.lock ./
-RUN bundle install
-
-COPY . .
-
-EXPOSE 4567
-CMD ["bundle", "exec", "middleman"]

README.md

@@ -20,13 +20,6 @@ This repository generates https://keepachangelog.com/.
 - `bundle install`
 - `bundle exec middleman` starts the local development server at http://localhost:4567
 
-### Docker
-
-- `git clone https://github.com/olivierlacan/keep-a-changelog.git`
-- `cd keep-a-changelog`
-- `docker build -t keep-a-changelog .`
-- `docker run -p 4567:4567 keep-a-changelog` starts the docker development server and binds it at http://localhost:4567
-
 ### Deployment
 
 - `bundle exec rake publish` builds and pushes to the `gh-pages` branch