Clean up README #649

Debug has a simple API with a handful of static-/member-methods. It has been relatively unchanged since its conception (yes, users of 0.x can most likely upgrade to the latest major without any problems).

However, the README currently reflects a manual (nay, a bible) of integrated examples, etc. for a library that should be easily grok-able in just a few moments' time.

Not every method call needs three examples, nor does it need several paragraphs explaining the intricacies of how the method is useful.

Further, the use of screenshots is egregious. They add several pagefuls of redundant information.

Let's minimize the README to just:

• Single screenshot (very top, centered)
• Title; summary
• Installation
• Basic usage
• API documentation
• Examples
• Open Collective et al
• License