Merge pull request #492 from SteveLauC/docs/run_RpcSystem

docs: remove usage of deprecated tokio_core in docs

capnp-rpc/src/lib.rs

@@ -164,8 +164,9 @@ pub trait VatNetwork<VatId> {
 /// will need to have more sophisticated `VatNetwork` implementations, in order to support
 /// [level 3](https://capnproto.org/rpc.html#protocol-features) features.
 ///
-/// An `RpcSystem` is a `Future` and needs to be driven by a task executor. A common way
-/// accomplish that is to pass the `RpcSystem` to `tokio_core::reactor::Handle::spawn()`.
+/// An `RpcSystem` is a non-`Send`able `Future` and needs to be driven by a task
+/// executor. A common way accomplish that is to pass the `RpcSystem` to 
+/// `tokio::task::spawn_local()`.
 #[must_use = "futures do nothing unless polled"]
 pub struct RpcSystem<VatId>
 where