Update docs

test/helpers/create2.js

@@ -0,0 +1,12 @@
+function computeCreate2Address (saltHex, bytecode, deployer) {
+  return web3.utils.toChecksumAddress(`0x${web3.utils.sha3(`0x${[
+    'ff',
+    deployer,
+    saltHex,
+    web3.utils.soliditySha3(bytecode),
+  ].map(x => x.replace(/0x/, '')).join('')}`).slice(-40)}`);
+}
+
+module.exports = {
+  computeCreate2Address,
+};