Release new version to PyPI

[resolritter]

The latest version on PyPI, 1.1.1, does not have commit c2c9800. Without that commit, files with the .opus extension are not supported, as also mentioned in #13 (comment). 1.1.1 works as follows:

$ replaygain sample.opus
sample.opus: not supported, ignoring it

With c2c9800 I am able to process the file as expected.