Define CallOpts type

src/contract_wrappers/token_wrapper.ts

@@ -17,6 +17,7 @@ import {
     CreateContractEvent,
     ContractEventEmitter,
     ContractEventObj,
+    CallOpts,
 } from '../types';
 
 const ALLOWANCE_TO_ZERO_GAS_AMOUNT = 47155;

src/types.ts

@@ -419,3 +419,7 @@ export interface Artifact {
         address: string;
     }};
 }
+
+export interface CallOpts {
+    defaultBlock?: Web3.BlockParam;
+}