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/src/main.rs

@@ -163,7 +163,7 @@ fn main() {
         0 => drain.filter_level(Level::Info),
         1 => drain.filter_level(Level::Debug),
         2 => drain.filter_level(Level::Trace),
-        _ => drain.filter_level(Level::Info),
+        _ => drain.filter_level(Level::Trace),
     };
 
     let mut log = slog::Logger::root(drain.fuse(), o!());