chore(package): update mocha to version 6.2.0

Closes #3

Author: greenkeeper[bot]

package.json

@@ -11,7 +11,7 @@
     "url": "[email protected]:revin/innertext.git"
   },
   "devDependencies": {
-    "mocha": "^4.0.0"
+    "mocha": "^6.2.0"
   },
   "keywords": [
     "html",