Remove Babel (#1074)

* Test helpers no longer rely on Babel.

* Behaviours are no longer imported.

* Removed Babel dependency.

* Fixed linter errors.

test/lifecycle/TokenDestructible.test.js

@@ -1,8 +1,7 @@
-import { ethGetBalance } from '../helpers/web3';
+const { ethGetBalance } = require('../helpers/web3');
 
 var TokenDestructible = artifacts.require('TokenDestructible');
 var StandardTokenMock = artifacts.require('StandardTokenMock');
-require('../helpers/transactionMined.js');
 
 contract('TokenDestructible', function (accounts) {
   let destructible;