chore(package): update standard-version to version 4.0.0 (#461)

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -116,7 +116,7 @@
     "source-map-support": "^0.4.6",
     "split-lines": "^1.0.0",
     "standard": "^8.0.0",
-    "standard-version": "^3.0.0",
+    "standard-version": "^4.0.0",
     "tap": "^8.0.0",
     "which": "^1.2.11",
     "zero-fill": "^2.2.3"