Update README

Add no_std support and update README

Create context tasks

Create System struct and basic example

Add task::from_fn

Add Then combinator and refactor

Start over with new design goals

Update example

Clean up and mark Scope::rebuild as unsafe

Impl basic async support

Create Scope::build, rebuild, and clear functions

Publish v0.19.0-alpha.2

Impl View for Option<V> and create use_on_drop hook

Add missing docs

Refactor and remove ActionResult enum