Add Exchange Proxy to Ganache snapshot (#2612)

* `@0x/contracts-zero-ex`: Expose migration tools.

* `@0x/contract-addresses`: Update ganache snapshot Exchange Proxy addresses

* `@0x/migrations`: Add Exchange Proxy migration

contracts/zero-ex/test/features/token_spender_test.ts

@@ -7,15 +7,11 @@ import {
 } from '@0x/contracts-test-utils';
 import { BigNumber, hexUtils, StringRevertError, ZeroExRevertErrors } from '@0x/utils';
 
+import { TokenSpenderContract, ZeroExContract } from '../../src/wrappers';
 import { artifacts } from '../artifacts';
 import { abis } from '../utils/abis';
 import { fullMigrateAsync } from '../utils/migration';
-import {
-    TestTokenSpenderERC20TokenContract,
-    TestTokenSpenderERC20TokenEvents,
-    TokenSpenderContract,
-    ZeroExContract,
-} from '../wrappers';
+import { TestTokenSpenderERC20TokenContract, TestTokenSpenderERC20TokenEvents } from '../wrappers';
 
 blockchainTests.resets('TokenSpender feature', env => {
     let zeroEx: ZeroExContract;