Add docs "Welcome" section

Taking a cue from a couple of other projects and a sudden urge to document more than just our framework components, I'm proposing a new docs section. It includes:

* Brief history of the framework
* List of team members
* Callout examples with uses
* Community and comms links

/cc @cvrebert @juthilo 

![screen shot 2013-09-08 at 6 34 35 pm](https://f.cloud.github.com/assets/98681/1104291/c8c2bfb2-18f0-11e3-86a8-74e7888b21c4.png)