Sigpropy

In this release

- 🎉 First stable release of _sigpropy_.
- ✨ Add support for Python 3.9.
- 🔒 Remove exec call for version.
- 💥 Rename master to main.
- 🎨 General updates to documentation.
- 🔧 Remove Python 3.8 from tox.
- 📚 Minor updates to the documentation.

In this release

- 💥 Remove `WindowedTimeSeries` and `FourierTransformSuite`.
- 🔨 Transfer all of the functionality of `WindowedTimeSeries` and `FourierTransformSuite` into `TimeSeries` and `FourierTransform`.
- ✨ Add `join` method to allow split `TimeSeries` to be recombined.
- ✨ Single source code's version using `__version__` in `meta.py`.
- ✅ Increase unit test coverage.
- 📚 General improvements to documentation throughout the package.

In this release

- ✨ Two new class definitions: `WindowedTimeSeries` and `FourierTransformSuite`.
- 🐎 Significant performance improvements to frequency-domain smoothing.
- 📚 Improvements to the project documentation including new additions to the example notebooks.
- ✅ Significantly increase test coverage.