Fix #126 (Use real templates)

source/_components/sensor.arest.markdown

@@ -31,8 +31,7 @@ sensor:
     A0:
       name: Pin 0 analog
       unit_of_measurement: "ca"
-      correction_factor: 0.01
-      decimal_places: 1
+      value_template: '{% raw %}{{ value_json.light }}{% endraw %}'
     3:
       name: Pin 3 digital
 ```
@@ -47,8 +46,7 @@ Configuration variables:
 - **pins** array (*Optional*): List of pins to monitor. Analog pins need a leading **A** for the pin number.
   - **name** (*Optional*): The name of the variable you wish to monitor.
   - **unit_of_measurement** (*Optional*): Defines the unit of measurement of the sensor, if any.
-  - **correction_factor** (*Optional*): A float value to do some basic calculations.
-  - **decimal_places** (*Optional*): Number of decimal places of the value.
+  - **value_template** (*Optional*): Defines a [template](/getting-started/templating/) to extract a value from the payload.
 
 The variables in the `monitored_variables` array must be available in the response of the device. As a starting point you could use the one of the example sketches (eg.  [Ethernet](https://raw.githubusercontent.com/marcoschwartz/aREST/master/examples/Ethernet/Ethernet.ino) for an Arduino with Ethernet shield). In those sketches are two variables (`temperature` and `humidity`) available which will act as endpoints. 
 
@@ -78,4 +76,3 @@ The root will give you a JSON response that contains all variables and their cur
 {"return_value": 34, "id": "sensor02", "name": "livingroom", "connected": true}
 ```
 
-