meta: add requirements, gitignore, and modify README

[mathemonads]

Addresses Leavingseason/xDeepFM/issues/16.

[yugam-aggarwal]

i used these commands and the code ran perfectly.

conda create -n xdeepfm-tf1 python=3.7 -y
conda activate xdeepfm-tf1

pip install --upgrade pip
pip install "tensorflow==1.15.5" "numpy==1.16.6" "scikit-learn==0.24.2" "PyYAML==5.4.1" "packaging==21.3" "protobuf==3.20.*"

cd exdeepfm
python -c "import tensorflow as tf; print(tf.version)"
python main.py