chore(package): update karma to version 3.1.0

Closes #14

Author: greenkeeper[bot]

package.json

@@ -24,7 +24,7 @@
     "grunt-contrib-concat": "^1.0.1",
     "grunt-contrib-uglify": "^3.0.0",
     "grunt-release-it": "^1.0.1",
-    "karma": "^2.0.2",
+    "karma": "^3.1.0",
     "karma-coverage": "^1.0.0",
     "karma-coveralls": "^1.1.2",
     "karma-mocha": "^1.0.1",