Update docker to the new adpater v2

[MatheusFaria]

Following the rocketchat/hubot-rocketchat-boilerplate, I've update the Dockerfile to use only the necessary packages. Also, the .travis.yml is now running the eslint, that is why the build is failing, and it pushes the docker image to docker hub on success. In order to make this work you need to configure at travis two env variables DOCKER_PASSWORD and DOCKER_USERNAME.

I've used the standard .eslintrc.js file, probably we should update it based on the community feedback.

Two things that I'm sending but I'm not sure:

1. I've deleted the pakage-lock.json, because otherwise the docker build was getting stuck on the npm install step. Since we have the docker version, I don't know if we have to maintain the lock in the repository.
2. I've removed the coffescript dependency, assuming that we don't need it anymore

[diegodorgam]

Awesome @MatheusFaria! Thks for this.

I'll take a look this weekend and try to merge it.

About the package-lock, we need it to keep track of all dependencies, and have github helping us checking if anyone of those has any security problem. It doesn't need to be copied to the Docker image, but it have to be in the repository root.

[MatheusFaria]

Got it, I'll update the PR later with the lock.