Tradfri (#2420)

* Added initial support for IKEA Tradfri (Trådfri) Gateway

* Added initial support for IKEA Tradfri (Trådfri) Gateway

source/_components/light.tradfri.markdown

@@ -0,0 +1,39 @@
+---
+layout: page
+title: "Tradfri (Trådfri) Gateway"
+description: "Access and control your ZigBee-based IKEA Tradfri (Trådfri) Lights."
+date: 2017-04-12 22.04
+sidebar: true
+comments: false
+sharing: true
+footer: true
+ha_category: Light
+ha_iot_class: "Local Polling"
+ha_release: 0.43
+---
+
+Support for the IKEA Tradfri (Trådfri) gateway. The gateway can control lights connected to it.
+
+NB: for this to work, you need to install the lib-coap library:
+```
+$ apt-get install libtool
+
+$ git clone --recursive https://github.com/obgm/libcoap.git
+$ cd libcoap
+$ git checkout dtls
+$ git submodule update --init --recursive
+$ ./autogen.sh
+$ ./configure --disable-documentation --disable-shared
+$ make
+$ sudo make install
+```
+
+To enable these lights, add the following lines to your `configuration.yaml` file:
+
+```yaml
+# Example configuration.yaml entry
+light:
+  - platform: tradfri
+    host: 192.168.0.129
+    api_key: <on back of gateway>
+```