chore(package): update ember-cli-babel to version 7.4.0

Closes #1733

Author: greenkeeper[bot]

package.json

@@ -25,7 +25,7 @@
     "ember-cli": "~2.18.0",
     "ember-cli-app-version": "^3.0.0",
     "ember-cli-autoprefixer": "0.8.1",
-    "ember-cli-babel": "^6.6.0",
+    "ember-cli-babel": "^7.4.0",
     "ember-cli-bourbon": "2.0.0-beta.1",
     "ember-cli-code-coverage": "^0.4.1",
     "ember-cli-dependency-checker": "^2.1.0",