Add destroy method to Flexslider.

- Supports multiple instances on a page.
Add destroy method information to the README
Fix notes
Fix notes (fin)
Fix notes (fin!)
I'll leave it to the Flexslider team if they want to host the demo from this branch
Improve the destroy method

- Remove flexslider generated elements when present
- Remove flexslider classes and generated styles on base flexslider elements
- Unbind all events by namespace
- Stop the flexslider time
- Also removed some unnecessary code from previous draft
Merge remote-tracking branch 'bradgreens/release-2-2-0'

Add "destroy"-method.