Update README

The README should have links to the latest source release and PyPi.
> In practice, the garbage collector *does* work. If you create a SoundFile object in some function, the file *will* be closed as soon as the function returns.

In your experience it may have worked so far, the current CPython implementation may do it as you expect, but all that doesn't matter!

What matters, is the language specification. Python is a bit weak regarding a formal specification, but as I mentioned in https://github.com/bastibe/PySoundFile/pull/14#issuecomment-36464595, all we need to know is described in https://docs.python.org/3.3/reference/datamodel.html:

> An implementation is allowed to postpone garbage collection or omit it altogether

and

>  It is not guaranteed that `__del__()` methods are called for objects that still exist when the interpreter exits.

I want to add another quote this time (emphasis mine):

> Some objects contain references to “external” resources such as open files or windows. It is understood that these resources are freed when the object is garbage-collected, but since garbage collection is not guaranteed to happen, such objects also provide an explicit way to release the external resource, usually a `close()` method. Programs are **strongly recommended to explicitly close such objects**. The `try`...`finally` statement and the `with` statement provide convenient ways to do this.

This is reason enough to recommend to our users to explicitly close `SoundFile` objects.
Not closing them *might* work in a specific situation, but its un-Pythonic nevertheless.

> I think that this is actually an important feature, and should be advertised as such.

It is un-safe and un-idiomatic and I suggest not to advertise it at all.

> I will change the specific wording

The new wording "... and closes when the object is garbage collected" might even be the truth!

But it's still highly misleading (you should write something like "if and when") and it encourages bad Python style.

I think we should try to educate our users towards good Pythonic programming, and it is very clear what's Pythonic in this case!