Update to Truffle 4.1.5 and Ganache 6.1.0 (#876)

* Update to ganache-cli v6.1.0 and truffle v4.1.0

* Update to stable version of ganache-cli

* fix: update event emission warning

- Fix event emission warnings for solidity 4.21 after truffle has been
updated to use this version

* fix pr review comments

* update to truffle v4.1.5

* update package-lock

* add additional emit keywords

* update solidity-coverage to 0.4.15

* update to solium 1.1.6

* fix MerkleProof coverage analysis by testing through wrapper

* change version pragma to ^0.4.21

* fix solium linting errors

test/library/MerkleProof.test.js

@@ -2,13 +2,13 @@
 import MerkleTree from '../helpers/merkleTree.js';
 import { sha3, bufferToHex } from 'ethereumjs-util';
 
-var MerkleProof = artifacts.require('MerkleProof');
+var MerkleProofWrapper = artifacts.require('MerkleProofWrapper');
 
 contract('MerkleProof', function (accounts) {
   let merkleProof;
 
   before(async function () {
-    merkleProof = await MerkleProof.new();
+    merkleProof = await MerkleProofWrapper.new();
   });
 
   describe('verifyProof', function () {