Update docs & demos post-API rework release

[derekpierre]

Follow-up to #560 . Depends on #568 , https://github.com/nucypher/sprints/issues/52

• [x] Once there is @nucypher/taco release with these changes, update the demos in the demos folder since they use a release version of the library, not the local one - https://github.com/nucypher/taco-web/pull/578
• [x] Update docs - https://app.gitbook.com/o/R2meumXNNad4y1B10iL7/s/WosjlL4zUGUMlcMfuSAp/~/changes/467

[derekpierre]

Docs work started here - https://app.gitbook.com/o/R2meumXNNad4y1B10iL7/s/WosjlL4zUGUMlcMfuSAp/~/changes/467.