Merge pull request #69 from ethereumjs/greenkeeper/ethereumjs-util-6.0.0

Update ethereumjs-util to the latest version 🚀

Author: holgerd77

package.json

@@ -28,7 +28,7 @@
     "ethashjs": "~0.0.7",
     "ethereumjs-block": "~2.0.1",
     "ethereumjs-common": "~0.6.0",
-    "ethereumjs-util": "~5.2.0",
+    "ethereumjs-util": "~6.0.0",
     "flow-stoplight": "^1.0.0",
     "levelup": "^1.3.2",
     "lru-cache": "^4.1.3",