chore(package): update ember-power-select to version 1.8.0

Closes #1252

https://greenkeeper.io/

package.json

@@ -76,7 +76,7 @@
     "ember-moment": "7.3.0",
     "ember-normalize": "1.0.0",
     "ember-page-title": "^3.1.2",
-    "ember-power-select": "1.6.1",
+    "ember-power-select": "1.8.0",
     "ember-radio-button": "^1.0.7",
     "ember-resolver": "^2.0.3",
     "ember-route-action-helper": "^2.0.0",