U.K.-based retailer John Lewis has leaked supposed details of the fourth-generation iPod touch at a recent event in London. Electricpig reports that a slide from the retailer’s Xmas in July event claimed that the fourth-generation iPod touch will arrive in September, and will sport a five megapixel camera with flash, similar to the one found in the iPhone 4 and including HD video recording capabilities, an accelerometer and gyroscope, and FaceTime…