There's a first for everything, including Engadget stories about software updates for thermostats. If we're going to suddenly start getting granular in our coverage of home automation products, though, we may as well start with the Nest, a device slick enough to make us use "thermostat" and "sexy' in the same sentence. Now that it's been out on the market for about five months, the company's issuing a software update that introduces a couple new features. For starters, particularly fastidious users can now access a detailed 10-day history, showing precisely when and for how lon