chore(package): update mocha to version 7.0.1

Closes #19

Author: greenkeeper[bot]

package.json

@@ -37,6 +37,6 @@
     "eslint-config-guo": "^0.5.0",
     "eslint-plugin-promise": "^3.5.0",
     "istanbul": "^0.4.5",
-    "mocha": "^4.0.0"
+    "mocha": "^7.0.1"
   }
 }