Remove ember-cli-babel dependency.

Since this addon has no code in `addon/` or `addon-test-support/` we do
not need a hard dependency on `ember-cli-babel` and it can be a dev
dependency just fine.

(cherry picked from commit 8adde8c)

package.json

@@ -23,6 +23,7 @@
   "devDependencies": {
     "ember-cli": "2.8.0",
     "ember-cli-app-version": "^1.0.0",
+    "ember-cli-babel": "^6.0.0-beta.7",
     "ember-cli-dependency-checker": "^1.2.0",
     "ember-cli-htmlbars": "^1.0.3",
     "ember-cli-htmlbars-inline-precompile": "^0.4.0-beta.2",
@@ -38,9 +39,7 @@
   "keywords": [
     "ember-addon"
   ],
-  "dependencies": {
-    "ember-cli-babel": "^6.0.0-beta.7"
-  },
+  "dependencies": { },
   "ember-addon": {
     "configPath": "tests/dummy/config"
   },