Merge pull request eclipse-archived#320 from kaikreuzer/yahoo-docs

added readme for Yahoo weather binding

addons/binding/org.eclipse.smarthome.binding.yahooweather/README.md

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+# YahooWeather Binding
+
+This binding uses the [Yahoo Weather service](https://developer.yahoo.com/weather/) for providing current weather information.
+
+_Note:_ The Yahoo Weather API is provided by Yahoo free of charge for personal, non-commercial uses, but it requires attribution and the acceptance of their terms of use.
+By using this binding, you confirm that you agree with this - please read the details on [https://developer.yahoo.com/weather/](https://developer.yahoo.com/weather/).
+
+## Supported Things
+
+There is exactly one supported thing, which represents the weather service. It has the id ```weather```.
+
+## Discovery
+
+The binding supports discovery, which does a geo location lookup based on the current IP address (using [freegeoip.net](http://freegeoip.net)).
+
+## Thing Configuration
+
+Besides the location (as ```location``` as a [WOEID](https://en.wikipedia.org/wiki/WOEID) number), the second configuration parameter is ```refresh``` which defines the refresh interval in seconds.
+
+## Channels
+
+The weather information that is retrieved is available as these channels:
+
+| Channel Type ID | Item Type    | Description  |
+|-----------------|------------------------|------------- |
+| temperature | Number       | The current temperature in degrees celsius |
+| humidity | Number       | The current humidity in % |
+| pressure | Number       | The current pressure in millibar (hPa) |
+
+
+## Full Example
+
+demo.things:
+```
+yahooweather:weather:berlin [ location="638242" ]
+```
+
+demo.items:
+```
+Number Temperature 	"Outside Temperature" { channel="yahooweather:weather:berlin:temperature" }
+```
+
+demo.sitemap:
+```
+sitemap demo label="Main Menu"
+{
+	Frame {
+		Text item=Temperature
+	}
+}
+```