Reworked audio test set.

- Decided it best to use the Creative Commons xeno-canto data
- Decided it best to stick to Screaming Piha audio to honor the package's name
- Had to update the Jupyter Notebook tutorial with the new dataset
- Deleted the audio, new update in the readme branch will link to a public drive with the relevant test set
- Replaced the old labels from the old test set with the labels for the new screaming piha dataset.