1. pip install tensorflow 不成功；
Could not find any downloads that satisfy the requirement tensorflow。
2. pip install --upgrade pip; pip install tensorflow 仍然不成功
3. export TF_BINARY_URL=https://storage.googleapis.com/tensorflow/linux/cpu/tensorflow-0.12.1-cp27-none-linux_x86_64.whl
sudo pip install --upgrade $TF_BINARY_URL成功
Refer to:
https://stackoverflow.com/questions/41875915/install-tensorflow-on-ubuntu-14-04;
https://morvanzhou.github.io/tutorials/machine-learning/tensorflow/1-2-install/;
https://www.tensorflow.org/install/install_linux.
