README updates

README.md

@@ -29,6 +29,8 @@ App.ApplicationAdapter = DS.FirebaseAdapter.extend({
 });
 ```
 
+You're Firebase data will now be synced with the Ember Data store
+
 You can now interact with the data store as you normally would. For example,
 calling `find()` with a specific ID will retrieve that record from Firebase.
 Additionally, from that point on, every time that record is updated in Firebase,
@@ -37,6 +39,95 @@ it will automatically be updated in the local data store.
 See the [Ember documentation](http://emberjs.com/guides/models/) for a full
 list of methods, including ways to create, find, delete and query records.
 
+### Relationships
+
+EmberFire can handle relationships in two different ways
+
+#### Async
+
+Any relationship that is flagged as `async: true` tells the adapter to fetch
+the record if it hasn't already been loaded
+
+```js
+App.Post = DS.Model.extend({
+  comments: DS.hasMany('comment', { async: true })
+});
+```
+
+In the `App.Post` example, comments will be fetched from
+`https://<my-firebase>.firebaseio.com/comments` 
+
+Here is what the data structure would look in Firebase:
+
+```json
+{
+  "posts": {
+    "-JIzst0Wbx-zjKKNtl8a": {
+      "comments": {
+        "-JIzsxCt35JEnay7AKY5": true
+      }
+    }
+  },
+  "comments": {
+    "-JIzsxCt35JEnay7AKY5": {
+      "body": "This is a comment"
+    }
+  }
+}
+```
+
+*\*The IDs used in the example are arbitrary*
+
+#### Embedded
+
+Any relationship that is flagged as `embedded: true` tells the adapter
+that the related records have been included in the payload.
+
+Generally, this approach is more complicated and not as widley used,
+but it has been included to support existing data structures.
+
+```js
+App.Post = DS.Model.extend({
+  comments: DS.hasMany('comment', { embedded: true })
+});
+```
+
+Here is what the data structure would look like in Firebase:
+
+```json
+{
+  "posts": {
+    "-JIzst0Wbx-zjKKNtl8a": {
+      "comments": {
+        "-JIzsxCt35JEnay7AKY5": {
+          "body": "This is a comment"
+        }
+      }
+    }
+  }
+}
+```
+
+**NOTE**: When a modal has embedded relationships, the related model
+can't be saved on it's own.
+
+```js
+var comment = store.createRecords('comment');
+// This won't work because the adapter doesn't know
+// where to save the comment without the context of the post
+comment.save();
+```
+
+Instead, the comment needs to be added to the post
+and then the post can be saved
+
+```js
+// Add the new comment to the post and save it
+post.get('comments').addObject(comment);
+// Saving the post will then save the embedded comments
+post.save()
+```
+
 ## Development
 
 If you would like to build EmberFire from the source, use grunt to build and lint the code: