Add climate.modbus module documentation (#4593)

* Added climate.modbus module documentation

* Update climate.modbus.markdown

Updated IOT class Local Push to Local Polling.

* Reviewed comments for changes

Added configuration tags, removed optional configuration values, and set the correct release version.

* Fixed formatting with the configuration settings

* ⬆️ ha_release -> 0.68

source/_components/climate.modbus.markdown

@@ -0,0 +1,70 @@
+---
+layout: page
+title: "Modbus"
+description: "Instructions how to integrate a Modbus thermostat within Home Assistant."
+date: 2018-01-29 9:35
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: modbus.png
+ha_category: Thermostat
+ha_release: 0.68
+ha_iot_class: "Local Polling"
+---
+
+
+The `modbus` thermostat allows you to use a sensor value (current temperature)
+and target value (target temperature) from [Modbus](http://www.modbus.org/)
+registers.
+
+To use your Modbus thermostat in your installation, add the following to your `configuration.yaml` file:
+
+```yaml
+climate:
+  - platform: modbus
+    name: Watlow F4T
+    slave: 1
+    target_temp_register: 2782
+    current_temp_register: 27586
+
+```
+
+{% configuration %}
+name:
+  description: Name of the device
+  required: true
+  type: string
+slave:
+  description: The number of the slave (Optional for tcp and upd Modbus, use 1).
+  required: true
+  type: int
+target_temp_register:
+  description: Register number for target temperature (Setpoint).
+  required: true
+  type: int
+current_temp_register:
+  description: Register number for current temperature (Process value).
+  required: true
+  type: int
+data_type:
+  description: Response representation (int, uint, float, custom). If float selected, value will converted to IEEE 754 floating point format.
+    Default float.
+  required: false
+  type: string
+count:
+  description: Number of registers to read.
+  required: false
+  type: int
+precision:
+  description: Number of valid decimals, default 0.
+  required: false
+  type: int
+{% endconfiguration %}
+
+
+### {% linkable_title Services %}
+
+| Service | Description |
+| ------- | ----------- |
+| set_temperature | Set Temperature. Requires `value` to be passed in, which is the desired target temperature. `value` should be in the same type as `data_type` |