Refactor block_processing

- Add the rayon library for parallelization
- Move from std::sync::Rwlock to rayon::RwLock
- Add `state` field to BeaconChain
- Fix major bug in attestation validator where justified slot was
incorrectly looked up.

beacon_node/beacon_chain/Cargo.toml

@@ -13,6 +13,7 @@ failure = "0.1"
 failure_derive = "0.1"
 genesis = { path = "../../eth2/genesis" }
 hashing = { path = "../../eth2/utils/hashing" }
+parking_lot = "0.7"
 log = "0.4"
 env_logger = "0.6"
 serde = "1.0"