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/helpers/increaseTime.js

@@ -1,6 +1,6 @@
 import latestTime from './latestTime';
 
-// Increases testrpc time by the passed duration in seconds
+// Increases ganache time by the passed duration in seconds
 export default function increaseTime (duration) {
   const id = Date.now();
 
@@ -25,7 +25,7 @@ export default function increaseTime (duration) {
 }
 
 /**
- * Beware that due to the need of calling two separate testrpc methods and rpc calls overhead
+ * Beware that due to the need of calling two separate ganache methods and rpc calls overhead
  * it's hard to increase time precisely to a target point so design your test to tolerate
  * small fluctuations from time to time.
  *