message: Update tokio version in feature docs
diff: //!
  //! | Feature | Description | Extra dependencies | Default |
  //! | ------- | ----------- | ------------------ | ------- |
  -//! | `runtime` | Enable convenience API for the connection process based on the `tokio` crate. | [tokio](https://crates.io/crates/tokio) 0.3 with the features `net` and `time` | yes |
  +//! | `runtime` | Enable convenience API for the connection process based on the `tokio` crate. | [tokio](https://crates.io/crates/tokio) 1.0 with the features `net` and `time` | yes |
  //! | `with-bit-vec-0_6` | Enable support for the `bit-vec` crate. | [bit-vec](https://crates.io/crates/bit-vec) 0.6 | no |
  //! | `with-chrono-0_4` | Enable support for the `chrono` crate. | [chrono](https://crates.io/crates/chrono) 0.4 | no |
  //! | `with-eui48-0_4` | Enable support for the `eui48` crate. | [eui48](https://crates.io/crates/eui48) 0.4 | no |
  