Split 0x.js into contract-wrappers, order-watcher but keep 0x.js as a unifying library with the same interface

packages/contract-wrappers/test/global_hooks.ts

@@ -0,0 +1,7 @@
+import { runMigrationsAsync } from '@0xproject/migrations';
+
+import { deployer } from './utils/deployer';
+
+before('migrate contracts', async () => {
+    await runMigrationsAsync(deployer);
+});