chore(package): update mocha to version 4.1.0

Closes #10

Author: greenkeeper[bot]

package.json

@@ -15,7 +15,7 @@
   "devDependencies": {
     "blue-tape": "^1.0.0",
     "chai": "^4.0.0",
-    "mocha": "^3.3.0",
+    "mocha": "^4.1.0",
     "onchange": "^3.2.1",
     "tap-spec": "^4.1.1",
     "ts-node": "^4.0.0",