Remake the README.md

[Reuh]

The README is almost the same as it was when we started the project, but ctrµLua is in an usable state now, so we need to make it more friendly to newcomers.
I think we should add:

• Add screenshots. Everybody loves screenshots.
• Hello world example.
• Getting started guide (how to install, the essentials modules, ctrµLua's organisation and how to read the docs).
• Remove this lie: "Everything is in the Wiki.". And we should probably remove everything outdated in the wiki too.
• Add an actual credits section.

[WhatNodyn]

There's an actual credits section. On the teeny blog but filling it alone is kinda hard.