Refactoring

[pabloos]

Hi there, here's some little refactorings

[arl]

Hey @pabloos thanks for your pull-request, that's much appreciated.

I've just finished and merged a pull-request I had started some time ago to improve the API, while remaining backward-compatible.
Some code has already been reorganized to improve readability/browse-ability.
Your PR has a lot of overlap with what I did.

Feel free to update your branch and propose another PR.
However the prototype of exported functions can't be changed since this would break compatibility.
Thanks again for your interest in statsviz

[pabloos]

Ouch! Thanks, I had just updated my fork. I'm going to do a review it and create another PR.

Good job and thank you again!