update usps doc (#1880)

source/_components/sensor.usps.markdown

@@ -12,7 +12,7 @@ ha_category: Sensor
 ha_release: 0.36
 ---
 
-The `usps` platform allows one to track deliveries by the [US Postal Service (USPS)](https://www.usps.com/).
+The `usps` platform allows one to track deliveries by the [US Postal Service (USPS)](https://www.usps.com/). You must opt-in to [MyUSPS](https://my.usps.com/mobileWeb/pages/intro/start.action) prior to using this sensor. Doing so will confirm your address.
 
 To enable this sensor, add the following lines to your `configuration.yaml`:
 
@@ -24,9 +24,24 @@ sensor:
     password: YOUR_PASSWORD
 ```
 
-Configuration options for the a TCP Sensor:
+Configuration options for the USPS Sensor:
 
-- **username** (*Required*): The username to access the USPS service.
+- **username** (*Required*): The username to access the MyUSPS service.
 - **password** (*Required*): The password for the given username.
-- **update_interval** (*Optional*): Interval in minutes for the updates.
+- **name** (*Optional*): Name the sensor (default: your mailing address).
+- **update_inverval** (*Optional*): Minimum time interval between updates. Default is 1 hour. Supported formats:
+  - `update_interval: 'HH:MM:SS'`
+  - `update_interval: 'HH:MM'`
+  - Time period dictionary, e.g.:
+    <pre>update_interval:
+        # At least one of these must be specified:
+        days: 0
+        hours: 0
+        minutes: 3
+        seconds: 30
+        milliseconds: 0
+    </pre>
 
+<p class='note warning'>
+The USPS sensor logs into the MyUSPS website to scrape package data. It does not use an API.
+</p>