chore(package): update mocha to version 7.1.1

Closes #48

Author: greenkeeper[bot]

Diff for: package.json

@@ -41,7 +41,7 @@
   "devDependencies": {
     "chai": "^4.1.2",
     "codecov": "^3.1.0",
-    "mocha": "^6.2.2",
+    "mocha": "^7.1.1",
     "nyc": "^15.0.0",
     "postcss": "^7.0.2",
     "postcss-safe-parser": "^4.0.1",