Update README.md

TensorFlow2Paddle/README.md

-### Warning: TensorFlow2Paddle is not stable and lots of tensorflow operations are not supported yet. Only tested on vgg_16/resnet_v1_50/inception_v3 with is_training=False
+### Warning
+> TensorFlow2Paddle is not stable and lots of tensorflow operations are not supported yet. 
+> Only tested on vgg_16/resnet_v1_50/inception_v3 with is_training=False
 
 ### Dependency
-1. python = 2.7
-2. PaddlePaddle >= 1.2.0
-3. TensorFlow >= 1.12.0
+> 1. python = 2.7
+> 2. PaddlePaddle >= 1.2.0
+> 3. TensorFlow >= 1.12.0
 
 Notice：You can install PaddlePaddle and Tensorflow in different virtual environment since there's dependency conflict between PaddlePaddle and TensorFlow