Add a script to install the Nvidia GDK on a host.

This script can be used to install the Nvidia GDK for Cuda 7.5 on a
mesos development machine. The purpose of the Nvidia GDK is to provide
all the necessary header files (nvml.h) and library files
(libnvidia-ml.so) necessary to build mesos with Nvidia GPU support.

If the machine on which Mesos is being compiled doesn't have any GPUs,
then libnvidia-ml.so consists only of stubs, allowing Mesos to build
and run, but not actually do anything useful under the hood. This
enables us to build a GPU-enabled mesos on a development machine
without GPUs and then deploy it to a production machine with GPUs and
be reasonably sure it will work.