Bw-temporalis

* Allow division of absolute temporal distributions by numbers. Needed for unusual distributions in supply chain.

* Add experimental node (instead of flow) timeline

* Add `Timeline.add_metadata_to_dataframe` method
* Removed `utils.supplement_dataframe` function

* Fix [11](https://github.com/brightway-lca/bw_temporalis/issues/11) - Support uncertainty in graph traversal propagating to temporal distributions

* Fix [22](https://github.com/brightway-lca/bw_temporalis/issues/22) - Add a warning when the number of steps is much higher than the possible resolution in `easy` functions
* Fix [10](https://github.com/brightway-lca/bw_temporalis/issues/10) - Support dynamic temporal distributions
* Fix [7](https://github.com/brightway-lca/bw_temporalis/issues/7) - Add warnings to readme

* Add `FixedTimeOfYearTD` and `FixedTD` distributions.
* Add structure for dynamic functions to override temporal distributions. Fixes [10](https://github.com/brightway-lca/bw_temporalis/issues/10).
* Add ability to serialize and deserialize temporal distributions and dynamic distribution functions.