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/examples/SampleCrowdsale.test.js

@@ -21,7 +21,7 @@ contract('SampleCrowdsale', function ([owner, wallet, investor]) {
   const CAP = ether(20);
 
   before(async function () {
-    // Advance to the next block to correctly read time in the solidity "now" function interpreted by testrpc
+    // Advance to the next block to correctly read time in the solidity "now" function interpreted by ganache
     await advanceBlock();
   });