Updated Dockerfile @arbrog

Updated Dockerfile to set python3 as default, following suggestion of @arbrog
junyanz#666 (comment)

docs/Dockerfile

@@ -1,13 +1,13 @@
-FROM nvidia/cuda:9.0-base
+FROM nvidia/cuda:10.1-base
 
 RUN apt update && apt install -y wget unzip curl bzip2 git
-RUN curl -LO http://repo.continuum.io/miniconda/Miniconda-latest-Linux-x86_64.sh
-RUN bash Miniconda-latest-Linux-x86_64.sh -p /miniconda -b
-RUN rm Miniconda-latest-Linux-x86_64.sh
+RUN curl -LO http://repo.continuum.io/miniconda/Miniconda3-latest-Linux-x86_64.sh
+RUN bash Miniconda3-latest-Linux-x86_64.sh -p /miniconda -b
+RUN rm Miniconda3-latest-Linux-x86_64.sh
 ENV PATH=/miniconda/bin:${PATH}
 RUN conda update -y conda
 
 RUN conda install -y pytorch torchvision -c pytorch
 RUN mkdir /workspace/ && cd /workspace/ && git clone https://github.com/junyanz/pytorch-CycleGAN-and-pix2pix.git && cd pytorch-CycleGAN-and-pix2pix && pip install -r requirements.txt
 
-WORKDIR /workspace
+WORKDIR /workspace