Use Docker image version 291 (pytorch#444)

Author: yf225

.circleci/config.yml

@@ -65,15 +65,8 @@ pytorch_tutorial_build_defaults: &pytorch_tutorial_build_defaults
       command: |
         set -e
 
-        # Get latest PyTorch docker image version
-        curl -O https://raw.githubusercontent.com/pytorch/pytorch/master/.circleci/config.yml
-        while read line; do
-          if [[ "$line" == *PyTorchDockerVersion* ]]; then
-            export pyTorchDockerImageTag=${line:23}  # len("# PyTorchDockerVersion:") == 23
-            echo "PyTorchDockerImageTag: "${pyTorchDockerImageTag}
-            break
-          fi
-        done < config.yml
+        export pyTorchDockerImageTag=291
+        echo "PyTorchDockerImageTag: "${pyTorchDockerImageTag}
 
         cat >/home/circleci/project/ci_build_script.sh <<EOL
         # =================== The following code will be executed inside Docker container ===================