Tidy BeaconChain; del spec, unify head updates

beacon_node/http_server/src/api.rs

@@ -10,6 +10,7 @@ use persistent::Read;
 use router::Router;
 use serde_json::json;
 use std::sync::Arc;
+use types::EthSpec;
 
 /// Yields a handler for the HTTP API.
 pub fn build_handler<T: BeaconChainTypes + 'static>(
@@ -64,7 +65,7 @@ fn handle_fork<T: BeaconChainTypes + 'static>(req: &mut Request) -> IronResult<R
 
     let response = json!({
         "fork": beacon_chain.head().beacon_state.fork,
-        "chain_id": beacon_chain.spec.chain_id
+        "chain_id": T::EthSpec::spec().chain_id
     });
 
     Ok(Response::with((Status::Ok, response.to_string())))