Merge pull request #5 from ericf/juandopazo-live-docs

Some fixes for Promise's user guide and examples
Add newlines at EOF, remove type attribute
Show table of contents
Capitalize titles and add missing links
Use node.set('text', text) instead of innerHTML
Incorporate @ericf's feedback

- Show markup and CSS in GutHub cache example
- Use Y.Lang.sub and Y.Escape.html
- Missing / in URL
Tests for the Node Plugin example
Tests for the GitHub cache example
Add test for subclass example

Make ArrayPromise#each chainable to allow for later error listening