[cpp-package]Update readme#8655 (#8746)

cpp-package/README.md

@@ -1,8 +1,12 @@
-# MxNet C++ Package
+# MXNet C++ Package
 
+<!--
 [![Build Status](https://travis-ci.org/dmlc/MXNet.cpp.svg?branch=master)](https://travis-ci.org/dmlc/MXNet.cpp)
 [![Build status](https://ci.appveyor.com/api/projects/status/ckfq6j53sg5ll01d/branch/master?svg=true)](https://ci.appveyor.com/project/lx75249/mxnet-cpp/branch/master)
+-->
 
-The examples dir containers examples for you to get started.
-The lib dir should contain the compiled mxnet library.
-Windows dir contains Visual C++ solution files and project files.
+To build the package, please refer to <https://mxnet.incubator.apache.org/get_started/build_from_source.html#build-the-c-package>.
+
+A basic tutorial can be found at <https://mxnet.incubator.apache.org/tutorials/c++/basics.html>.
+
+The example directory contains examples for you to get started. 

cpp-package/example/feature_extract/README.md

@@ -0,0 +1,8 @@
+This example shows how to extract features with a pretrained model.
+
+You can first get a pretrained model from <https://github.com/dmlc/mxnet-model-gallery/blob/master/imagenet-1k-inception-bn.md>,
+then prepare 2 pictures 1.jpg and 2.jpg to extract by executing `run.sh`.
+
+Note:
+1. The filename of network parameters may vary, line 67 in `feature_extract.cpp` should be updated accordingly.
+2. As the build system has changed a lot, to build this example, you need to put the compiled library `libmxnet.so` in `../lib/linux`.