Fix broken model fetch link

As stated at issue #1602 currently model link has been broken.
This commit addresses the problem by suggesting alternative model link
that maintainer provided.

So, in here, we used the supplementary package 'gdown' to download
google drive files.

models/getModels.sh

@@ -1,3 +1,29 @@
+# ------------------------- Downlaod MODELS -------------------------
+# (ISSUE #1602) Maintainer has provided alternative model link with google drive.
+# https://github.com/CMU-Perceptual-Computing-Lab/openpose/issues/1602#issuecomment-641653411
+MODEL_URL="https://drive.google.com/uc?id=1QCSxJZpnWvM00hx49CJ2zky7PWGzpcEh"
+FILENAME='models.zip'
+
+# Supplementary package 'gdown' to download google drive
+if ! [ -x "$(command -v gdown)" ]; then
+    echo "Please install gdown package with pip"
+    exit
+fi
+
+cd ..
+gdown ${MODEL_URL} -O ${FILENAME}
+unzip ${FILENAME}
+cd -
+
+RESULT=$?
+if [ $RESULT -eq 0 ]; then
+  echo "Model download success"
+  exit
+else
+  echo "Model download failure"
+  echo "Fallback to original approach"
+fi
+
 # ------------------------- BODY, FOOT, FACE, AND HAND MODELS -------------------------
 # Downloading body pose (COCO and MPI), face and hand models
 OPENPOSE_URL="http://posefs1.perception.cs.cmu.edu/OpenPose/models/"