chore(package): update ember-source to version 3.8.0

Closes #69

Author: greenkeeper[bot]

package.json

@@ -53,7 +53,7 @@
     "ember-resolver": "^5.0.0",
     "ember-sinon": "^2.1.0",
     "ember-sinon-qunit": "^3.3.0",
-    "ember-source": "~3.3.0",
+    "ember-source": "~3.8.0",
     "ember-source-channel-url": "^1.0.1",
     "ember-try": "^1.0.0",
     "eslint-plugin-ember": "^5.0.0",