If count exceeds SoundStream data range, only read to data range end

This pull request is associated with Issue #312.

I have also prepared a few unit tests, where I have added a WAV file to the unit test project to verify the correctness of the fix. If you want me to, I can include the unit test commit in this pull request, otherwise I'll wait for you to accept or reject this request until I upload anything else to my fork.

Best regards,
Anders @ Cureos