chore(package): update truffle to version 5.0.2

Closes #80

Author: greenkeeper[bot]

package.json

@@ -77,7 +77,7 @@
     "solc": "^0.4.24",
     "solidity-coverage": "^0.5.5",
     "solium": "^1.1.8",
-    "truffle": "^4.1.13",
+    "truffle": "^5.0.2",
     "truffle-hdwallet-provider": "0.0.7-beta.1",
     "truffle-privatekey-provider": "^1.0.0",
     "utf8-bytes": "0.0.1"