v0.3.0

Updated to use swift-atomics v1.0.1+.
Cleaned up some code and removed things deprecated in v0.2.0.
This will likely become v1.0.0.

v0.2.0

Major refactor to more closely match Swift 5.5's continuation types that support transforming callback code to async/await.

v0.1.0

More README.md udpates