chore(package): update mocha to version 6.1.3

Closes #63

Author: greenkeeper[bot]

package.json

@@ -43,7 +43,7 @@
     "jsdom": "^11.0.0",
     "leaflet": "1.0.3",
     "leaflet-draw": "^0.4.9",
-    "mocha": "^3.2.0",
+    "mocha": "^6.1.3",
     "style-loader": "^0.18.0",
     "url-loader": "^0.5.7",
     "webpack": "^3.1.0",