Extends the README docs by a tutorial with use cases & FAQ

[plokhotnyuk]

Tutorial should contain code snippets with printed results.

Checking of code snippets need to be some how automated using tut or alternatives.

It is need show typical and rare use cases, explain performance hints, highlight somehow a security cheat-sheet, and and evolution guidelines, FAQ section for most frequent questions.

See some inspiring articles: http://seriot.ch/parsing_json.php http://vasters.com/blog/data-encodings-and-layout/ https://stackify.com/top-11-json-performance-usage-tips/