Use case insensitive grep for Temp lines

xorg-x11-drv-nvidia-340.29-1.el6.x86_64 (CUDA 6.5?) seems to have changed the Temperature lines from "Gpu" to "GPU" prefixes. Case insensitive grep preserves backwards comatability.
Merge pull request #525 from leeclemens/patch-3

Use case insensitive grep for Temp lines