chore(package): update truffle-contract to version 4.0.8

Closes #62

Author: greenkeeper[bot]

package.json

@@ -27,7 +27,7 @@
     "ethereumjs-wallet": "0.6.2",
     "ganache-core": "2.2.1",
     "mocha": "5.1.1",
-    "truffle-contract": "3.0.6",
+    "truffle-contract": "4.0.8",
     "web3": "0.20.6"
   },
   "dependencies": {