Added a onClosed and my suggestion for a fix on #105

Hi,

Please check / accept my pull request.

I've added a option called 'onClosed' to use if the close button is pressed. Also I saw a filed bug (issue #105) which I thought you could fix it by removing the handler for the mouseleave event, after clicking the remove button.

I tested this on the latest version of Chrome and Firefox, also on IE10 and IE11. Not sure how you expect contributions because I didn't find them on the docs, cause after running grunt your comments from css where removed and some changes where made. 

Regards Dave