Added an Outline

Added an outline for the overview content. This mostly focuses
on why you might not want to use Koding for a production host.
Production vs What Is

Moved the Production Host? bit into it's own section, and used
the "What Is Koding?" section to focus on that question.
Exploiting Note, and Removed PaaS CPU Info

Added an exploiting note, since @devrim mentioned that i figured
it should be included.

Also, removed the bit about how other cloud hosts run their show.
Focusing instead on Koding solely.
Andys Comments

Andy has begun reviewing the document, let the nitpicking begin!

*(Only kidding @andygold99, thank you :)*
Typos

Fixing a few more typos.
Merge pull request #38 from leeolayvar/whatiskoding-guide

What is Koding, Overview