Downgraded mocha to ^2.3.3.

Author: Giedrius Grabauskas

package.json

@@ -34,7 +34,7 @@
     "typescript": "^1.8.10"
   },
   "devDependencies": {
-    "mocha": "^3.0.0",
+    "mocha": "^2.3.3",
     "rimraf": "^2.5.4",
     "rollup": "^0.34.3",
     "rollup-plugin-typescript": "^0.7.7"