Added docs for Russound RNET support (#669)

* Added docs for Russound RNET

* Added russound.gif logo

source/_components/media_player.russound_rnet.markdown

@@ -0,0 +1,58 @@
+---
+layout: page
+title: "Russound RNET"
+description: "Instructions on how to integrate Russound RNET devices into Home Assistant."
+date: 2016-07-21 22:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: russound.gif
+ha_category: Media Player
+ha_release: 0.25
+---
+
+The `russound_rnet` platform allows you to control Russound devices that make use of the RNET protocol.
+
+This has initially been tested against a Russound CAV6.6 unit with six zones and six sources.
+
+Connecting to the Russound device is only possible by TCP, you can make use of a TCP to Serial gateway such as [tcp_serial_redirect](https://github.com/pyserial/pyserial/blob/master/examples/tcp_serial_redirect.py)
+
+To add a device to your installation, add the following to your `configuration.yaml` file:
+
+```yaml
+# Example configuration.yaml entry
+media_player:
+  platform: russound_rnet
+  host: 192.168.1.10
+  port: 1337
+  name: Russound
+  zones:
+    1:
+      name: Main Bedroom
+    2:
+      name: Living Room
+    3:
+      name: Kitchen
+    4:
+      name: Bathroom
+    5:
+      name: Dining Room
+    6:
+      name: Guest Bedroom
+  sources:
+    - name: Sonos
+    - name: Sky+
+    - name: iPod
+    - name: Unused 1
+    - name: Unused 2
+    - name: Kodi
+```
+
+Configuration variables:
+
+- **host** (*Required*): The IP of the TCP gateway
+- **port** (*Required*): The port of the TCP gateway
+- **name** (*Required*): The name of the device
+- **zones** (*Required*): This is the list of zones available
+- **sources** (*Required*): The list of sources available, these must be in order as they are connected to the device