Update "Retrieving the snapshot" code snipbit in docs (angular#334)

* Fixed af.databasse.list "Retrieving the snapshot"

While I discovered that including `import 'rxjs/add/operator/do';` made the previous example compile, it still didn't give me the snapshot.

The code I'm committing works with angularfire2 : ^2.0.0-beta.2

* Update "Retrieving the snapshot" example

typeof snapshot.key === 'string'. I was also naive enough to believe that it was snapshot.value() so I included the snapshot.val() in the example as well.

Author: cweidinger

docs/2-retrieving-data-as-objects.md

@@ -176,7 +176,10 @@ AngularFire2 unwraps the Firebase DataSnapshot by default, but you can get the d
 
 ```ts
 this.item = af.database.object('/item', { preserveSnapshot: true });
-this.item.subscribe(snapshot => console.log(snapshot.key()));
+this.item.subscribe(snapshot => {
+  console.log(snapshot.key)
+  console.log(snapshot.val())
+});
 ```
 
 ## Querying?

docs/3-retrieving-data-as-lists.md

@@ -196,10 +196,12 @@ AngularFire2 unwraps the Firebase DataSnapshot by default, but you can get the d
 ```ts
 this.items = af.database.list('/items', { preserveSnapshot: true });
 this.items
-  .do(snapshots => {
-    snapshots.forEach(snapshot => console.log(snapshot.key()));
+  .subscribe(snapshots => {
+    snapshots.forEach(snapshot => {
+      console.log(snapshot.key)
+      console.log(snapshot.val())
+    });
   })
-  .subscribe(snapshots => console.log(snapshots.length));
 ```
 
 ###[Next Step: Querying lists](4-querying-lists.md)