Documentation for APNS (#905)

* added documentation for APNS

* added link to Apple docs and corrected date

source/_components/notify.apns.markdown

@@ -0,0 +1,55 @@
+---
+layout: page
+title: "APNS"
+description: "Instructions how to add APNS notifications to Home Assistant."
+date: 2016-09-05 23:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+ha_category: Notifications
+---
+
+
+The `APNS` platform uses the Apple Push Notification service (APNS) to deliver notifications from Home Assistant.
+
+To use the APNS service you will need an apple developer account
+and you will need to create an App to receive push notifications.
+For more information see the apple developer documentation.
+
+```yaml
+# Example configuration.yaml entry
+notify:
+  name: NOTIFIER_NAME
+  platform: apns
+  sandbox: true or false
+  cert_file: cert_file.pem
+```
+
+Configuration variables:
+
+- **name** (*Required*): The name of the notifier. The notifier will bind to the service `notify.NOTIFIER_NAME`.
+- **sandbox** (*Optional*): If true notifications will be sent to the sandbox (test) notification service. Default false.
+- **cert_file** (*Required*): The certificate to use to authenticate with the APNS service.
+
+ The APNS platform will register two services, `notify.NOTIFIER_NAME` and `apns.NOTIFIER_NAME`.
+
+### apns.NOTIFIER_NAME
+
+This service will register device id's with home assistant. In order to receive a notification a device must be registered. The app on the device can use this service to send an id to Home Assistant during startup, the id will be stored in `[NOTIFIER_NAME]_apns.yaml`.
+
+See didRegisterForRemoteNotificationsWithDeviceToken in the [Apple developer documentation](https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIApplicationDelegate_Protocol/#//apple_ref/occ/intfm/UIApplicationDelegate/application:didRegisterForRemoteNotificationsWithDeviceToken:) for more information about how to obtain a device id.
+
+### notify.NOTIFIER_NAME
+
+This service will send messages to a registered device. The following parameters can be used:
+
+- **message**: The message to send
+
+- **target**: The desired state of the device, only devices that match the state will receive messages. To enable state tracking a registered device must have a `tracking_device_id` attribute added to the `[NOTIFIER_NAME]_apns.yaml` file. If this id matches a device in known_devices.yaml the device state will be tracked.
+
+- **data**:
+	* **badge**: The number to display as the badge of the app ic
+	* **sound**: The name of a sound file in the app bundle or in the Library/Sounds folder.
+	* **category**: Provide this key with a string value that represents the identifier property of the UIMutableUserNotificationCategory
+	* **content_available**: Provide this key with a value of 1 to indicate that new content is available.