Update README.md

onnx2fluid/README.md

@@ -25,7 +25,7 @@ conda install -c conda-forge onnx
 ```shell
 python -m onnx2fluid -e -o /path/to/export/model /path/of/onnx/model
 ```
-### VGG19转换
+**VGG19转换**
 ```shell
 # 下载并解压onnx模型vgg19
 wget https://s3.amazonaws.com/download.onnx/models/opset_9/vgg19.tar.gz