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

eth2/lmd_ghost/src/reduced_tree.rs

@@ -8,7 +8,7 @@ use parking_lot::RwLock;
 use std::collections::HashMap;
 use std::marker::PhantomData;
 use std::sync::Arc;
-use store::{iter::BlockRootsIterator, Error as StoreError, Store};
+use store::{iter::BestBlockRootsIterator, Error as StoreError, Store};
 use types::{BeaconBlock, BeaconState, EthSpec, Hash256, Slot};
 
 type Result<T> = std::result::Result<T, Error>;
@@ -530,14 +530,14 @@ where
         Ok(a_root)
     }
 
-    fn iter_ancestors(&self, child: Hash256) -> Result<BlockRootsIterator<E, T>> {
+    fn iter_ancestors(&self, child: Hash256) -> Result<BestBlockRootsIterator<E, T>> {
         let block = self.get_block(child)?;
         let state = self.get_state(block.state_root)?;
 
-        Ok(BlockRootsIterator::owned(
+        Ok(BestBlockRootsIterator::owned(
             self.store.clone(),
             state,
-            block.slot,
+            block.slot - 1,
         ))
     }