util/async: documentation
index.md: adding reference to async doc
async doc: adding callback ref

Added a line to indicate how the callback is called. i.e. with zero
parameters and null context (global context in ES3).
async doc: fixing up hash reference for github
Updating docs to have short descriptions
util/extend docs
trait/pubsub docs
Class documentation converted to unix line ending
pubsub docs add clarification on listenTo context
pubsub docs minor formatting fixup
util/pipe docs
Remove todo about tests from readme. It's done!
util/diff docs
Model docs and minor fixes

Fixes are for registering the proper async diff check.
Model docs codeblock to demonstrate async diff
Model docs link fixup
Merge pull request #14 from Aintaer/master

A bunch of documentation