[Testing] Add unit tests.

[clarkzinzow]

Add unit tests for the following:

1. Shuffler (shuffle.py)
2. BatchQueue (batch_queue.py)
3. ShufflingDataset (dataset.py)
4. TorchShufflingDataset (torch_dataset.py)

Implementation Notes

• ShufflingDataset and TorchShufflingDataset testing could initially be as simple as running the example in the main block of dataset.py and torch_dataset.py, respectively, although these don't do much to assert correctness of the yielded batches.
• See these tests for easily portable examples for testing BatchQueue.

[krfricke]

I'll start with setting up CI and running examples, and then will add unit tests that also assert correctness.

• Shuffler (Unit tests for shuffler #22)
• BatchQueue (Add unit tests for batch queue #21)
• ShufflingDataset (Add GitHub actions workflow to run examples in CI #19, Fix CI: Lint, requirements #20)
• TorchShufflingDataset (Add GitHub actions workflow to run examples in CI #19, Fix CI: Lint, requirements #20)