[feature request] make tab closable

[tylerlong]

I like KSTabview, it's beatiful and just works.

A feature I am missing is : make the tabs closable. Just like a web browser tab. Add a small close button to the tab, when user click the close button, a delegate event should be sent.

[kaunteya]

Good suggestion. I will try to implement it. A pull request would be much appreciated !!!