Fix syncing bugs by recursively attempting to process parents in the … (#429)

* Fix syncing bugs by recursively attempting to process parents in the import queue, change BlockRootsIterator

* Swap from crossbeam channel to tokio mpsc

* Recursion fix

* Remove exess block processing

* Fix network lag, correct attestation topic

* Correct network poll logic

* Overhaul of SimpleSync and modify BlockRootsIterator to return start_slot

* Fix bug in tests relating to StateRootsIterator

* Remove old, commented-out heartbeat code.

* Tidy docs on import queue enum

* Change source logging msg in simple sync

* Rename function parameter in simple sync

* Use `BestBlockRootsIterator` in `reduced_tree`

* Update comments for `BestBlockRootsIterator`

* Fix duplicate dep in cargo.toml

beacon_node/rpc/src/lib.rs

@@ -20,11 +20,12 @@ use protos::services_grpc::{
 use slog::{info, o, warn};
 use std::sync::Arc;
 use tokio::runtime::TaskExecutor;
+use tokio::sync::mpsc;
 
 pub fn start_server<T: BeaconChainTypes + Clone + 'static>(
     config: &RPCConfig,
     executor: &TaskExecutor,
-    network_chan: crossbeam_channel::Sender<NetworkMessage>,
+    network_chan: mpsc::UnboundedSender<NetworkMessage>,
     beacon_chain: Arc<BeaconChain<T>>,
     log: &slog::Logger,
 ) -> exit_future::Signal {