Add Docker development workflow

[pataquets]

Add Docker workflow for making easier to start hacking. No devel packages nor development libs installation needed on development host, just Docker and Docker Compose and you're ready to go. People familiar with Docker will figure out themselves
Run:

$ docker-compose up --build

Stop by CTRL+C'ing.

Manifest launches a MariaDB server container based on mariadb[:latest] image and a collectd+python runtime container built from my pataquets/collectd-python-pip base image which just adds the necessary configs to send all collectd readings to stdout using the CSV plugin (see Dockerfile). Both containers are linked to allow collectd to connect to db via the mysql hostname.
The collectd container mounts from the Docker host's git repo directory:

• The Python program file.
• The mysql.conf config file.

Just hack, change confs and test by CTRL+C and up'ing again. Rinse and repeat.

This is what I've used so far to start tinkering and getting warm to tackle opened issues, some opened by me (#25, #27, #28). Hopefully, it will also help others interested in them to jump in and get up to speed quickly. HTH.

[pataquets]

@chrisboulton : Bump, in case you didn't get any notification.

[pataquets]

@chrisboulton : ping