chore(package): update mocha to version 6.0.2

Closes #23

Author: greenkeeper[bot]

package.json

@@ -34,7 +34,7 @@
     "chai": "^3.5.0",
     "istanbul": "^0.4.5",
     "memdown": "^1.0.0",
-    "mocha": "^3.2.0",
+    "mocha": "^6.0.2",
     "pouchdb": "^6.0.0"
   }
 }