how do you keep it warm enough in the winter? I got some starter grains in-line less than two weeks ago. I realize the temperature in my house is around 58-62. Too cool for kefir to grow. I contacted the company and they suggested putting it in the oven with the light on. I'm trying that right now but hate to waste the electricity, plus I'm afraid someone will accidentally turn the oven on. They also suggested putting it on top of a cable tv box or wifi router. I'm checking the temp of what I have to see if its warm enough. anyone else have any creative, inexpensive ideas on keeping a consistent, warm temp?