chore(package): update karma to version 2.0.0

Author: greenkeeper[bot]

package.json

@@ -26,7 +26,7 @@
   "homepage": "https://github.com/jimmywarting/FormData#readme",
   "devDependencies": {
     "chai": "^4.1.2",
-    "karma": "^1.7.1",
+    "karma": "^2.0.0",
     "karma-chai": "^0.1.0",
     "karma-chrome-launcher": "^2.2.0",
     "karma-mocha": "^1.3.0",