Add docs for USPS sensor (#1722)

source/_components/sensor.usps.markdown

@@ -0,0 +1,32 @@
+---
+layout: page
+title: USPS Sensor
+description: "Instructions on how to set up USP sensors within Home Assistant."
+date: 2017-01-06 08:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: usps.png
+ha_category: Sensor
+ha_release: 0.36
+---
+
+The `usps` platform allows one to track [US POstal Service (USPS)](https://www.usps.com/).
+
+To enable this sensor, add the following lines to your `configuration.yaml`:
+
+```yaml
+# Example configuration.yaml entry
+sensor:
+  - platform: usps
+    username: YOUR_USERNAME
+    password: YOUR_PASSWORD
+```
+
+Configuration options for the a TCP Sensor:
+
+- **username** (*Required*): The username to access the USPS service.
+- **password** (*Required*): The password for the given username.
+- **update_interval** (*Optional*): Interval in minutes for the updates.
+