Add some documentation how to drive this thing

[oherrala]

What should I do to make changes? How do I locally test changes?

[oherrala]

Maybe something like this:

1. bundler install
2. jekyll serve
3. browse to http://127.0.0.1:4000/

Update Gemfile.lock:

1. bundler update

[evilon]

Related to #2 and #27