message: add tensorflow downgrade instructions
diff: @@ -23,12 +23,20 @@ Getting Started
  Install Tensorflow
  ------------------
  Start by installing Tensorflow and the dependencies, optionally into a
  -virtualenv if you so choose. This should be as simple as
  +virtualenv if you so choose. First:
  ```
  pip3 install -r requirements.txt
  ```
  +Then, you must either install CUDA 8.0 (See Tensorflow documentation) or downgrade
  +to non-gpu tensorflow. To downgrade:
  +
  +```
  +pip3 uninstall tensorflow-gpu
  +pip3 install tensorflow
  +```
  +
  Running unit tests
  ------------------
  ```
  