Update Dockerfile

Dockerfile

-FROM yoanlin/opencv-python3:latest
+FROM tensorflow/tensorflow:2.0.0a0-gpu-py3
 RUN apt-get update
 RUN pip install --upgrade pip
-RUN pip install tensorflow==2.0.0-beta1 
 RUN pip install numpy scipy scikit-learn pillow h5py keras 
 RUN pip install --upgrade imutils 
 RUN pip install --upgrade scikit-learn