Add Docker image, Makefile and requirements.txt

[juniorxsound]

Why?
Adding a Docker image based on the Tensorflow Docker image to create the installation and setup process easy and breezy.

What?
Adding Dockerfile.gpu which can easily be called using a Makefile that has the following commands:

• make build build the docker container
• make example run the pretained_example.py in the container
• make shell open bash inside the container
• make jupyter to run jupyter notebooks inside the container (would love to add notebook examples in a separate PR)

The setup uses the latest version of nvidia-docker and requires Docker 19.03 or newer

[frankcarey]

There is an error if you try to use the make jupyter command after make build because there is no ./notebooks directory. You need to either create it using mkdir notebooks or this PR could ship with a README.md in a new ./notebooks directory?

[juniorxsound]

Thanks @frankcarey, I have a bunch of example notebooks but feel like it might be a better idea to separate the examples into a PR since it might grow to be a larger change. I'll get rid of make jupyter for this PR and add to the next one