docs(CHANGELOG): add breaking change note about packaging

Author: jeffbcross

CHANGELOG.md

@@ -17,7 +17,27 @@
 * **utils:** Add $exists method to AFUnwrappedSnapshot ([#471](https://github.com/angular/angularfire2/issues/471)) ([f67aab1](https://github.com/angular/angularfire2/commit/f67aab1))
 * upgrade to RC7 ([#505](https://github.com/angular/angularfire2/issues/505)) ([2410b2d](https://github.com/angular/angularfire2/commit/2410b2d))
 
+### BREAKING CHANGES
+
+The way this project is packaged has changed to be consistent with other Angular packages.
+Previously:
+
+ * The project just consisted of CommonJS modules, with `angularfire2.js` as the main entry point.
+ * The project provided an `es6` directory which contained es2015 modules and es2015 JS
+ * Package.json included `main` and `jsnext:main` fields, pointing to `angularfire2.js` and `es6/angularfire2.js`, respectively.
+
+Now:
+
+ * The project ships ES2015 modules with ES5 JS at the root, as well as an ES5 UMD bundle at `bundles/angulafire2.umd.js`
+ * The `main` field of `package.json` points to `bundles/angularfire2.umd.js`.
+ * Instead of `jsnext:main`, we're using the `module` field of package.json to point to `index.js`.
+ * Instead of `angularfire2.js` being the main entry point, an `index.js` has been added (though angulafire2.js hasn't changed significantly).
+
+If you're using Rollup or Webpack, they should _just work_ with this new setup (please open issues if not). If using SystemJS, you should be able to
+add `format: 'esm'` inside of the packages configuration, and it should load and parse the es2015 modules correctly.
 
+The addition of the umd bundle will also make it possible to use AngularFire2 in a `<script>` tag, such as in a plunker or JSBin. The library is
+exported on a global called `angularFire2`.
 
 <a name="2.0.0-beta.4"></a>
 # [2.0.0-beta.4](https://github.com/angular/angularfire2/compare/2.0.0-beta.2...v2.0.0-beta.3) (2016-08-22)
@@ -77,7 +97,7 @@ apps are configured, and how third-party oauth tokens are handled.
 ## Breaking Changes:
  * [Upgrade to the Firebase 3.0+ SDK](https://firebase.google.com/docs/web/setup), versions less than 3.0 are not supported. [abe11a2](https://github.com/angular/angularfire2/pull/200/commits/abe11a2fd8f5a3f554056625b751e9308e56b906)
  * `defaultFirebase` takes in a configuration object rather than a database url string. [See docs for more info.](https://github.com/angular/angularfire2/blob/master/docs/1-install-and-setup.md)
- * Access tokens for third party auth (github, google, facebook, twitter) are not persisted after refresh. 
+ * Access tokens for third party auth (github, google, facebook, twitter) are not persisted after refresh.
 
 # AngularFire2 2.0.0-beta.0