[pkg] Update mocha to version 6.2.0 (#35)

package.json

@@ -28,6 +28,6 @@
     "concat-stream": "~2.0.0",
     "derequire": "~2.0.3",
     "istanbul": "~0.4.5",
-    "mocha": "~6.1.0"
+    "mocha": "~6.2.0"
   }
 }