Chore: upgrade mocha

Author: mysticatea

package.json

@@ -18,7 +18,7 @@
     "codecov": "^2.3.0",
     "eslint": "^4.7.2",
     "eslint-config-mysticatea": "^12.0.0",
-    "mocha": "^3.0.2",
+    "mocha": "^4.0.0",
     "nyc": "^11.2.1",
     "opener": "^1.4.1",
     "rimraf": "^2.5.4"