v. 2.1.0 - Use strict, rewrite Ajax Helper

- restructure the framework
- use strict
- rewrite Ajax Helper
- Velveto.ajax is now available as public method
- Velveto.fireEvent is now available as public method
- Ajax helper now support all HTTP Methods (e.g. Velveto.ajax.DELETE(),
Velveto.ajax.HEAD())
- remove unused script in Velveto.scroll()
- rename Velveto.scroll() to Velveto.scrollTo()