chore(package): update @ember/optional-features to version 1.2.0

Closes #91

Author: greenkeeper[bot]

package.json

@@ -35,7 +35,7 @@
     "hammer-timejs": "^1.1.0"
   },
   "devDependencies": {
-    "@ember/optional-features": "^0.6.3",
+    "@ember/optional-features": "^1.2.0",
     "broccoli-asset-rev": "^3.0.0",
     "ember-cli": "~3.4.3",
     "ember-cli-dependency-checker": "^3.0.0",