chore(package): update bs58 to version 4.0.0

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -28,7 +28,7 @@
   "dependencies": {
     "async": "^2.1.4",
     "bl": "^1.1.2",
-    "bs58": "^3.1.0",
+    "bs58": "^4.0.0",
     "chai": "^3.5.0",
     "concat-stream": "^1.5.2",
     "detect-node": "^2.0.3",