fixed tree_hash() for Vec<T> and a couple of other issues

beacon_chain/types/src/shard_and_committee.rs

@@ -29,7 +29,7 @@ impl TreeHash for ShardAndCommittee {
         result.append(&mut self.shard.tree_hash());
         result.append(&mut merkle_hash(&mut committee_ssz_items));
 
-        result.tree_hash()
+        result.as_slice().tree_hash()
     }
 }
 

beacon_chain/types/src/validator_record.rs

@@ -77,7 +77,7 @@ impl TreeHash for ValidatorRecord {
         balance.resize(16, 0);
         ssz.append(&mut balance);
 
-        ssz.tree_hash()
+        ssz.as_slice().tree_hash()
     }
 }