Add min/max sensor docs (#1232)

source/_components/sensor.min_max.markdown

@@ -0,0 +1,45 @@
+---
+layout: page
+title: "Min/max Sensor"
+description: "Instructions how to integrate min/max sensors into Home Assistant."
+date: 2016-10-13 12:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: home-assistant.png
+ha_category: Sensor
+ha_iot_class: "Local Polling"
+ha_release: "0.31"
+---
+
+
+The `min_max` sensor platform is consuming the state from other sensors and determine the minimum, maximum, and the mean of the collected states. The sensor will always show you the highest/lowest value which was received from your all monitored sensors. If you have spikes in your values, it's recommanded filter/equalize your values with a [statistics sensor](/components/sensor.statistics/) first.
+
+It's an alternative to the [template sensor](/components/sensor.template/)'s `value_template:` to get the average of multiple sensors.
+
+```yaml
+{% raw %}{{ ((float(states.sensor.kitchen_temperature.state) + 
+     float(states.sensor.living_room_temperature.state) +
+     float(states.sensor.office_temperature.state)) / 3) | round(2)
+}}{% endraw %}
+```
+
+To enable the minimum/maximum sensor, add the following lines to your `configuration.yaml`:
+
+```yaml
+# Example configuration.yaml entry
+sensor:
+  - platform: min_max
+    entity_ids:
+      - sensor.kitchen_temperature
+      - sensor.living_room_temperature
+      - sensor.office_temperature
+```
+
+Configuration variables:
+
+- **entity_ids** (*Required*): At least two entities to monitor
+- **type** (*Optional*): The type of sensor. Defaults to `max`.
+- **name** (*Optional*): Name of the sensor to use in the frontend.
+