Added 'opened' and 'closed' events when sections are opened/closed

Opened/Closed events are extremely useful, and I believe used in the reveal plugin.  It would be nice to have them in the section plugin.  Actually, I thought Foundation already had opened/closed events for several of the section types (accordion in particular), but maybe that was Foundation 3.

This works in my project using my private fork, so I thought I would share it for others that could use a reveal like section system.  There may be a better way to add these events, and somebody more involved with the development of Foundation might do a better job.  So I will not take any offense if this is rejected.

Also, please let me know if there is a testing framework.  I could not find one, but would be happy to write tests for this too.