Added code syntax highlighting for tutorials

[matustuhy]

Introduction

Added Code syntax highlighting to for tutorials

Motivation

Make it easier to read

[ricardograca]

Thanks for this, but there's a small problem. These tutorials aren't meant to be read separately, although that works. They are meant to be included in the website and that is generated using JSDoc, that's why you see the {@link Model#belongsToMany belongsToMany} stuff when you see the files on their own.

That said, it is acceptable to use GitHub flavoured markdown for syntax highlighting, but then you also have to remove the 4 spaces indentation of those blocks, otherwise the alignment is off.

[ricardograca]

Much better. Thanks!