PyTorch 1.6.0 update with native AMP (#573)

Dockerfile

 # Start FROM Nvidia PyTorch image https://ngc.nvidia.com/catalog/containers/nvidia:pytorch
 FROM nvcr.io/nvidia/pytorch:20.03-py3
-RUN pip install -U gsutil
+
+# Install dependencies
+COPY requirements.txt .
+RUN pip install -r requirements.txt gsutil
 
 # Create working directory
 RUN mkdir -p /usr/src/app
@@ -9,9 +12,6 @@ WORKDIR /usr/src/app
 # Copy contents
 COPY . /usr/src/app
 
-# Install dependencies (pip or conda)
-#RUN pip install -r requirements.txt
-
 # Copy weights
 #RUN python3 -c "from models import *; \
 #attempt_download('weights/yolov5s.pt'); \