Cleanup unused dependencies (#61)

* Remove unused "ember-welcome-page" addon

* Remove unused "ember-data" dependency

* Remove unused "ember-cli-release" dependency

* Remove unused "ember-cli-app-version" dependency

* Remove unused "ember-ajax" dependency

package.json

@@ -56,24 +56,19 @@
   "license": "MIT",
   "devDependencies": {
     "broccoli-asset-rev": "^2.4.2",
-    "ember-ajax": "^2.5.6",
     "ember-cli": "^2.12.1",
-    "ember-cli-app-version": "^3.0.0",
     "ember-cli-dependency-checker": "^1.4.0",
     "ember-cli-htmlbars": "^1.3.0",
     "ember-cli-htmlbars-inline-precompile": "^0.4.4",
     "ember-cli-inject-live-reload": "^1.4.0",
     "ember-cli-jshint": "^2.0.1",
     "ember-cli-qunit": "^3.1.2",
-    "ember-cli-release": "^1.0.0-beta.2",
     "ember-cli-sri": "^2.1.0",
     "ember-cli-uglify": "^1.2.0",
-    "ember-data": "^2.12.2",
     "ember-disable-prototype-extensions": "^1.1.0",
     "ember-export-application-global": "^2.0.0",
     "ember-load-initializers": "^1.0.0",
     "ember-resolver": "^4.1.0",
-    "ember-welcome-page": "^3.0.0",
     "eslint": "^3.19.0",
     "eslint-config-airbnb": "^14.1.0",
     "eslint-plugin-dollarshaveclub": "^1.0.0",