Add API stream sensor docs (#1462)

source/_components/sensor.api_stream.markdown

@@ -0,0 +1,24 @@
+---
+layout: page
+title: "API Stream Sensor"
+description: "Instructions how to count clients using the API stream within Home Assistant."
+date: 2016-11-19 10:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: home-assistant.png
+ha_category: Sensor
+ha_release: 0.33
+---
+
+The `api_stream` sensor platform shows how many clients are connected to the stream API 
+
+To add the connected clients to your installation, add the following to your `configuration.yaml` file:
+
+```yaml
+# Example configuration.yaml entry
+sensor:
+  - platform: api_streams
+```
+