Added select2-close event to index.html.

Added select2-close: Fired after the dropdown is closed.

Also fixed zebra striping in the events.
Added select2-close event to select2-latest.html

Added select2-close: Fired after the dropdown is closed.

Also fixed zebra striping in events section.
Merge pull request #2202 from mattjanssen/patch-1

Documentation: Added select2-close event to index and select2-latest.