WLAN widget

This widget monitors your WLAN's signal strength. To set the device it monitors, use
    obvious.wlan.set_device(dev)
The default is "wlan0". Specify "auto" to use the first available WLAN in your system.

To add it to your rc.lua, include
    require("obvious.wlan")
in the top of your rc.lua and add obvious.wlan().widget to your wibox

If you want to use the data gathered by this widget, you can use the function
obvious.wlan.get_data(). It returns nil on failure, otherwise it returns a table with
the field 'link' as its only content. That field contains a number the range of which
depends on the wlan driver and firmware used which describes the signal strength.
