170620 How to install tensorflow with GPU on linux

# step1: create a tensorflow-gpu environment
conda create -n tesorflow-gpu python=3.6

# step2: activate the  tensorflow-gpu environment
source activate tensorflow-gpu

# step3: install the .whl (if you have a loccal .whl file)
pip install --ignore-installed --upgrade + .whl path
# or (if you want to download the .whl file)
pip install tensorflow-gpu
# tensorflow can be imported in cmd window but can't be imported in Spyder.
# So we need to take the following step.

# step4: change to the desktop and install tensorflow with command line
pip insatll tensorflow     # install tensorflow (cpu-version)
pip install tensorflow-gpu # install tensorflow (gpu-version)