chore(package): update mocha to version 4.1.0

Closes #56

Author: greenkeeper[bot]

package.json

@@ -41,7 +41,7 @@
     "es3ify": "^0.2.2",
     "istanbul": "^0.4.5",
     "jshint": "^2.9.4",
-    "mocha": "^3.2.0",
+    "mocha": "^4.1.0",
     "phantomjs-prebuilt": "^2.1.7",
     "pouchdb-memory": "^6.0.0",
     "uglify-js": "^2.4.13",