Fix/docker and webpacker

[drewpotter]

This is the initial work to fix docker webpacker support.

[drewpotter]

I have spent a little bit of time this weekend thinking about and trying to fix the hot reloading for webpacker; I have pushed some changes again which will require:

docker-compose up --build

To make sure you get the ENV vars correctly in docker you can try the following command to check:

docker-compose run web /bin/bash -l -c 'echo "$NODE_ENV"'

You should see development is eventually outputted by this command. Also the same for this:

docker-compose run web /bin/bash -l -c 'echo "$RAILS_ENV"'