Update API docs and demos for recent worker improvements.

1. Can you list the "plethora of reasons"? The spec already enumerated *all* situations that prevent a worker from being GC'd, and I think none of them apply to a decent deflate library. I think a indefinite loop is the only realistic type of bug in a deflate library that can fail the GC, but such bugs already fails deflate/inflate in the first place. If browsers' GC systems have bug, not much we can do.

2. Users should call .close(), but it is very hard to ensure this for JS coders. To help coders to manager resources, C++ has RAII, Objective-C has ARC, Java has try-with-resources, C# has using statement, but JS has *nothing*. Even I am not sure that I did *all* the necessay .close() in my project.

3. Because JS has nothing to help coders to manager resources, most (if not all) web APIs don't require explictly closing resources, think about `FileReader` and `XMLHttpRequest`. So for advanced users who understand this, yes, they will rely on GC, and treat explictly closing (such as Worker.terminate()) as an optimazition/fine-tuning.