chore(package): update ember-cli to version 2.8.0

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -23,7 +23,7 @@
     "broccoli-stew": "^1.2.0",
     "broccoli-uglify-js": "^0.2.0",
     "broccoli-watchify": "^0.2.0",
-    "ember-cli": "2.7.0",
+    "ember-cli": "2.8.0",
     "ember-publisher": "0.0.7",
     "git-repo-version": "0.4.0",
     "json3": "^3.3.2",