Update Actix, Tokio -> 0.2 and Futures ->0.3

[geofmureithi-zz]

This PR attempts to update to the latest versions of rlua, actix, tokio and features.

• [x] Update Dependencies
• [x] Update Tests
• [ ] Ensure Tests are running

[geofmureithi-zz]

Only one test doesn't pass: https://stackoverflow.com/questions/63202694/rust-thread-panics-as-expected-but-test-doesnt-pass

@poga care to assist and hopefully merge

[yjhmelody]

@geofmureithi Maybe you can wait for tokio 1.0. But seem this project has no maintainer.