Update API docs and demos for recent worker improvements.

1. Why a deflate library needs a timer that runs forever? Even if there is one, there should be an option to disable the timer.

2. Refcounting is not reliable. If users forget a single .close() call, or any codes before before a .close() call throws, the entire refcounting is defeated.

3. Even if we document it as you suggested, advanced users who have read the code and unserstand web worker will come to the same conclusion as I currently documented.