changed Dockerfiles to clone r1.13.0 branch instead of master

Author: TannerGilbert

docker/cpu/Dockerfile

@@ -7,14 +7,15 @@ RUN apt-get update && \
 RUN apt-get install -y git
 
 # Installing the Tensorflow Object Detection API (https://gilberttanner.com/blog/installing-the-tensorflow-object-detection-api)
-RUN git clone --depth 1 https://github.com/tensorflow/models.git
+RUN git clone --depth 1 -b r1.13.0 https://github.com/tensorflow/models.git
 
 # Install object detection api dependencies
 RUN DEBIAN_FRONTEND=noninteractive apt-get install -y protobuf-compiler python3-pil python3-lxml python3-tk && \
     pip install Cython && \
     pip install contextlib2 && \
     pip install jupyter && \
     pip install matplotlib && \
+    pip install Pillow && \
     pip install tensorflow==1.14.0
 
 # Install pycocoapi

docker/gpu/Dockerfile

@@ -9,14 +9,15 @@ RUN apt-get install -y python3 && apt-get install -y python3-pip
 RUN update-alternatives --install /usr/bin/python python /usr/bin/python3.6 1
 
 # Installing the Tensorflow Object Detection API (https://gilberttanner.com/blog/installing-the-tensorflow-object-detection-api)
-RUN git clone --depth 1 https://github.com/tensorflow/models.git
+RUN git clone --depth 1 -b r1.13.0 https://github.com/tensorflow/models.git
 
 # Install object detection api dependencies
 RUN DEBIAN_FRONTEND=noninteractive apt-get install -y protobuf-compiler python3-pil python3-lxml python3-tk && \
     pip3 install Cython && \
     pip3 install contextlib2 && \
     pip3 install jupyter && \
     pip3 install matplotlib && \
+    pip3 install Pillow && \
     pip3 install tensorflow==1.14.0
 
 # Install pycocoapi