chore(package): update mocha to version 7.1.0

Closes #49

Author: greenkeeper[bot]

package.json

@@ -30,7 +30,7 @@
     "eslint": "^5.0.0",
     "gitbook-cli": "^2.3.2",
     "gitbook-plugin-include-codeblock": "^3.0.0",
-    "mocha": "^6.1.4",
+    "mocha": "^7.1.0",
     "npm-run-all": "^4.0.0",
     "power-assert": "^1.3.1",
     "textlint": "^11.0.0",