v0.9.0

* Disregard non-audio files when looking for impulse response files

* Remember randomized/chosen effect parameters. This allows for freezing the parameters and applying the same effect to multiple sounds. Use transform.freeze_parameters() and transform.unfreeze_parameters() for this.
* Fix a bug in ClippingDistortion where the min_percentile_threshold was not respected as expected.
* Implement transform.serialize_parameters(). Useful for when you want to store metadata on how a sound was perturbed.
* Switch to a faster convolve implementation. This makes AddImpulseResponse significantly faster.
* Add a rollover parameter to Shift. This allows for introducing silence instead of a wrapped part of the sound.
* Expand supported range of librosa versions
* Add support for flac in AddImpulseResponse
* Implement AddBackgroundNoise transform. Useful for when you want to add background noise to all of your sound. You need to give it a folder of background noises to choose from.
* Implement AddShortNoises. Useful for when you want to add (bursts of) short noise sounds to your input audio.
* Improve handling of empty input