Fix tslint issues

packages/0x.js/src/0x.ts

@@ -61,7 +61,7 @@ export class ZeroEx {
      * ERC721 proxy smart contract.
      */
     public erc721Proxy: ERC721ProxyWrapper;
-    private _contractWrappers: ContractWrappers;
+    private readonly _contractWrappers: ContractWrappers;
     /**
      * Generates a pseudo-random 256-bit salt.
      * The salt can be included in a 0x order, ensuring that the order generates a unique orderHash

packages/0x.js/test/global_hooks.ts

@@ -7,7 +7,7 @@ before('migrate contracts', async function(): Promise<void> {
     // HACK: Since the migrations take longer then our global mocha timeout limit
     // we manually increase it for this before hook.
     const mochaTestTimeoutMs = 20000;
-    this.timeout(mochaTestTimeoutMs);
+    this.timeout(mochaTestTimeoutMs); // tslint:disable-line:no-invalid-this
     const txDefaults = {
         gas: devConstants.GAS_LIMIT,
         from: devConstants.TESTRPC_FIRST_ADDRESS,