chore(package): update ember-concurrency to version 1.1.5

Closes #1755

Author: greenkeeper[bot]

package.json

@@ -62,7 +62,7 @@
     "ember-cli-uglify": "^2.0.0",
     "ember-click-outside": "^0.1.10",
     "ember-composable-helpers": "2.1.0",
-    "ember-concurrency": "^0.8.1",
+    "ember-concurrency": "^1.1.5",
     "ember-data": "~2.18.0",
     "ember-disable-proxy-controllers": "^1.0.1",
     "ember-dragula": "1.9.3",