libp2p-noise 0.20.0

Cryptographic handshake protocol using the noise framework.
Documentation 
# 0.20.0 [2020-07-01]

- Updated dependencies.
- Conditional compilation fixes for the `wasm32-wasi` target
  ([PR 1633](https://github.com/libp2p/rust-libp2p/pull/1633)).

# 0.19.1 [2020-06-22]

- Re-add noise upgrades for IK and IX
  ([PR 1580](https://github.com/libp2p/rust-libp2p/pull/1580)).

- Updated dependencies.