I was reading about how to cool the raspberry pi, I plan to do so, however, some articles mentioned that I should use a buffer circuit rather than connecting it directly into the GPIO pins. What does this mean and how do a find out if fan that works with it (is there a size limit or voltage limit)? Also, how do I keep the fan in place, should I use thermal paste to glue the fan to a heat sink? I am using a rpi2.