Add config file

@monodo, I had some kind of an idea this night...

This PR adds a `config.yaml` file to the application.

In this file, we will be able to modify quite easily the resolution regarding if a code is passed through the request (or not), thus, two possible situations:
* The code is passed through the request: we can use a longer line and a more width buffer if wanted.
* The code is not in the request params: we used some default values.

Could you review this PR and tell me if you agree?