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Currently our test suites automatically/silently skip tests on C++ extension
if it is not available. This is nice in local env, but in CI these tests should be
enforced and reported as failure if C++ extension is not available.

This PR adds switch for making tests fail if C++ extension is not available,
and make CI for *nix fail if that's the case.

buck gets confused with utility module name with `test_` prefix.

* Add sox_utils module

* Make init/shutdown thread safe

* Add sox effects implementation

* Add test for sox effects

* Update docstrings and add examples