set_light_temp: Set a light to a specific color temperature and brightness
In acartauchenius/rhue: R to Philipps Hue connector

This function does not check if the light actually has the capability to change color temperature, Lamp metadata, obtainable by get_light_data should contain that information.

1	set_light_temp(bridge_url, user, light_id, kelvin, brightness)

`bridge_url`	Hue bridge URL E.g. "http://192.168.1.100"
`user`	user id, to be obtained by `create_user`
`light_id`	used to address a specific light. Can be looked up by `dump_lights_data`
`kelvin`	color temperature in Kelvin
`brightness`	brightness (number between 0 and 1)