Add unit test coverage to noise_module.py

[carlosgjs]

See: https://app.codecov.io/gh/noisepy/NoisePy/blob/main/src%2Fnoisepy%2Fseis%2Fnoise_module.py

Here's how to get coverage locally:

pytest tests --cov --cov-report=html:covrep
open covrep/index.html