Cuda install for paperspace

The current bash script that installs the environment on paperspace machines might be missing a step. The script pulls in cuda 9.1 but does not modify $PATH to pick up cuda9.1/bin. cuda9.1 is linked off to just cuda in /usr/local, so I suggest something like this to get the tools:

export PATH=/usr/local/cuda/bin${PATH:+:${PATH}}