This is the first `alpha` release of version `1.13.0`.
The focus of this release is to expand the use-cases supported by the Cadence mechanism.
* updates dependencies from Django 3.1.1 to Django 3.1.2
* defined `DynamicCadence` class to associate `CadenceStrategy` with `ObservationGroup`
* refactored `CadenceForm` class to support arbitrary cadence parameters
* dev-ops enhancements in `flake8` and `coveralls`