Use runmd to build README

[broofa]

https://github.com/broofa/runmd is a new module I've been working on that allows you to evaluate JS code blocks in README (and other markdown) files. Benefits of this:

1. Hooking it into the publish process (via npm 'prepare' script hook) acts as a unit test of sorts. Publish doesn't happen if the README file can't be built, so there's incentive to insure the README file is kept current.
2. It can automatically inject expression results into the markdown, which makes including expected output in docs easier
3. It forces authors to write code that is accurate and runnable instead of copy/pasting/guessing (cough not that I've ever done that.)

Thoughts?

[MikeyBurkman]

Need to aslo fix the /v4 part of this line as well

[defunctzombie]

sure, why not tho I am a bit sad of the use of var over const in the README now.