Docker/docker-compose enhancements

The following enhancements have been made to docker/docker-compose

* Fixed bug when building the image.
* docker-compose up starts the server
* Scaffolding inside the container respect the ownership of the files
outside it
* Volumes are tagged as 'delegated' in order to improve performance for
mac/windoze users.
* bundler stores packages in a volume. This whay new packages can be
added without rebuilding the image:

```bash
docker-compose run app bundle install
```

Dockerfile

@@ -1,8 +1,17 @@
-# # Select ubuntu as the base image
-FROM coreapps/ruby2.3
+FROM ruby:2.3.6
 
 # Install essential Linux packages
-RUN apt-get update -qq && apt-get install -y build-essential libpq-dev postgresql-client nodejs imagemagick
+RUN apt-get update -qq && apt-get install -y build-essential libpq-dev postgresql-client nodejs imagemagick sudo
+
+# Files created inside the container repect the ownership
+RUN adduser --shell /bin/bash --disabled-password --gecos "" consul \
+  && adduser consul sudo \
+  && echo '%sudo ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers
+
+RUN echo 'Defaults secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/bundle/bin"' > /etc/sudoers.d/secure_path
+RUN chmod 0440 /etc/sudoers.d/secure_path
+
+COPY scripts/entrypoint.sh /usr/local/bin/entrypoint.sh
 
 # Define where our application will live inside the image
 ENV RAILS_ROOT /var/www/consul