Update handbook package.json

Author: Baylee Swenson

lib/handbook/package.json

@@ -8,8 +8,8 @@
     "@ember/render-modifiers": "*",
     "ember-angle-bracket-invocation-polyfill": "*",
     "ember-bootstrap": "*",
-    "ember-changeset": "^2.1.2",
-    "ember-changeset-validations": "^2.1.0",
+    "ember-changeset": "*",
+    "ember-changeset-validations": "*",
     "ember-cli-addon-docs": "*",
     "ember-cli-addon-docs-typedoc": "*",
     "ember-cli-babel": "*",
@@ -18,10 +18,11 @@
     "ember-cli-typescript": "*",
     "ember-code-snippet": "*",
     "ember-component-attributes": "*",
-    "ember-content-placeholders": "https://github.com/cos-forks/ember-content-placeholders#master#2018-07-19",
+    "ember-content-placeholders": "*",
     "ember-cp-validations": "*",
     "ember-css-modules": "*",
     "ember-css-modules-sass": "*",
+    "ember-event-helpers": "*",
     "ember-font-awesome": "*",
     "ember-on-modifier": "*",
     "ember-onbeforeunload": "*",