@0x/contracts-exchange: Light refactoring in

`isolated_fill_order.ts` and `isolated_exchange_wrapper.ts`.

contracts/exchange/test/isolated_fill_order.ts

@@ -46,14 +46,18 @@ blockchainTests('Isolated fillOrder() tests', env => {
 
     before(async () => {
         [takerAddress, notTakerAddress] = await env.getAccountAddressesAsync();
-        exchange = await IsolatedExchangeWrapper.deployAsync(
-            env.web3Wrapper,
-            _.assign(env.txDefaults, { from: takerAddress }),
-        );
+        exchange = await IsolatedExchangeWrapper.deployAsync(env.web3Wrapper, {
+            ...env.txDefaults,
+            from: takerAddress,
+        });
     });
 
     function createOrder(details: Partial<Order> = {}): Order {
-        return _.assign({}, DEFAULT_ORDER, { salt: new BigNumber(nextSaltValue++) }, details);
+        return {
+            ...DEFAULT_ORDER,
+            salt: new BigNumber(nextSaltValue++),
+            ...details,
+        };
     }
 
     interface FillOrderAndAssertResultsResults {

contracts/exchange/test/utils/isolated_exchange_wrapper.ts

@@ -11,7 +11,6 @@ import { BigNumber } from '@0x/utils';
 import { TxData, Web3Wrapper } from '@0x/web3-wrapper';
 import * as crypto from 'crypto';
 import { LogEntry } from 'ethereum-types';
-import * as _ from 'lodash';
 
 import {
     artifacts,
@@ -105,7 +104,7 @@ export class IsolatedExchangeWrapper {
             verifyingContractAddress: this.instance.address,
             chainId: IsolatedExchangeWrapper.CHAIN_ID,
         };
-        return orderHashUtils.getOrderHashHex(_.assign(order, { domain }));
+        return orderHashUtils.getOrderHashHex({ ...order, domain });
     }
 
     public async getOrderInfoAsync(order: Order): Promise<OrderInfo> {