Include Create React Native App in Getting Started

Summary:
cc hramos

Create React Native App was designed to reduce "time to hello world" to 5-10 minutes for React Native apps. This PR would make CRNA the first way to get started that new users encounter. Included also is some text to help advanced users navigate the question of whether to use CRNA or whether to go straight to `react-native init`. It also includes a new banner for the iOS and Android guides, since they do not apply to CRNA users.

Changes are only to the website, screenshots below. This branch was created from the last CI-passing master commit this morning, dependencies were freshly installed and these screenshots are from a clean build.

[The Getting Started page](https://www.dropbox.com/s/1s7f3wu3oxr6gpo/Screenshot%202017-04-04%2015.12.29.png?dl=0)

[The "native builds only" banner](https://www.dropbox.com/s/nyv51xdiibdkn57/Screenshot%202017-04-04%2015.13.25.png?dl=0)

[Pages which still apply to CRNApps have no banner](https://www.dropbox.com/s/qgl0h6uzynqkmy2/Screenshot%202017-04-04%2015.14.10.png?dl=0)

<details>

* [x] Decide how to handle native code & react-native-cli references outside of the `banner: ejected` guides
  * [x] [Debugging: Accessing Console Logs](https://facebook.github.io/react-native/docs/debugging.html#accessing-console-logs) isn't needed in CRNA (logs are forwarded alongside packager output)
  * [x] [Debugging: With Stetho](https://facebook.github.io/react-native/docs/debugging.html#debugging-with-stetho-http-facebook-github-io-stetho-on-android) requires native code
  * [x] [Debugging: Debugging Native Code](https://facebook.github.io/react-native/docs/debugging.html#debugging-native-code) is native-only
  * [x] [AppRegistry](https://facebook.github.io/react-native/docs/appregistry.html) only applies to ejected apps, since this is generated from code, I don't think we can set `banner: ejected`?
  * [x] [Linking](https://facebook.github.io/react-native/docs/linking.html) involves changing Android manifests and other native-side things
  * [x] [PermissionsAndroid](https://facebook.github.io/react-native/docs/permissionsandroid.html) may be flaky in the Expo client, I can't recall (cc jesseruder)
  * [x] [PushNotificationIOS](https://facebook.github.io/react-native/docs/pushnotificationios.html) won't work inside Expo, as it has to [handle its own push notifs](https://docs.expo.io/versions/v15.0.0/guides/push-notifications.html)
  * [x] [Geolocation](https://facebook.github.io/react-native/docs/geolocation.html) requires a polyfill that will most likely ship with next week's release, but that won't have any manifest changes necessary
* [ ] Figure out a strategy to handle the fact that CRNA will lag stable RN releases by ~1 week
* [x] Confirm linking out to CRNA docs is an OK strategy as opposed to moving ejecting, etc. docs in-tree
* [ ] Answer questions (I'll add some review comments to call out a few things)

</details>
Closes https://github.com/facebook/react-native/pull/13303

Differential Revision: D4950661

Pulled By: hramos

fbshipit-source-id: 3dd43828f38ca6ede3f2b0683608c56420dc6525

Libraries/PushNotificationIOS/PushNotificationIOS.js

@@ -58,11 +58,22 @@ export type PushNotificationEventName = $Enum<{
 }>;
 
 /**
+ * <div class="banner-crna-ejected">
+ *   <h3>Projects with Native Code Only</h3>
+ *   <p>
+ *     This section only applies to projects made with <code>react-native init</code>
+ *     or to those made with Create React Native App which have since ejected. For
+ *     more information about ejecting, please see
+ *     the <a href="https://github.com/react-community/create-react-native-app/blob/master/EJECTING.md" target="_blank">guide</a> on
+ *     the Create React Native App repository.
+ *   </p>
+ * </div>
+ *
  * Handle push notifications for your app, including permission handling and
  * icon badge number.
  *
  * To get up and running, [configure your notifications with Apple](https://developer.apple.com/library/ios/documentation/IDEs/Conceptual/AppDistributionGuide/AddingCapabilities/AddingCapabilities.html#//apple_ref/doc/uid/TP40012582-CH26-SW6)
- * and your server-side system. To get an idea, [this is the Parse guide](https://parse.com/tutorials/ios-push-notifications).
+ * and your server-side system.
  *
  * [Manually link](docs/linking-libraries-ios.html#manual-linking) the PushNotificationIOS library
  *