Snuggly, cheap, and so efficient at warming that it’s a legit lower-carbon form of heating — Yesterday I caught the flu. I hadn’t gotten my flu shot. (Don’t be like me: Get your flu shot if you can, folks!) Anyway, by the evening my fever spiked to 101.4 and I was a shivery, chilly, achy mess. I went to bed to get warm, but it wasn’t…