Update README.md
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- libraries:
- bzip2-devel 1.0.6: boost depend it
+ - zlib-devel
The **build.sh** script will automatically download and build the dependency libraries including libevent, json and boost. It will save libraries under rocketmq-client-cpp folder, and then build both static and shared libraries for rocketmq-client. If the dependent libraries are built failed, you could try to build it manually with sources [libevent 2.0.22](https://github.com/libevent/libevent/archive/release-2.0.22-stable.zip "lib event 2.0.22"), [jsoncpp 0.10.6](https://github.com/open-source-parsers/jsoncpp/archive/0.10.6.zip "jsoncpp 0.10.6"), [boost 1.58.0](http://sourceforge.net/projects/boost/files/boost/1.58.0/boost_1_58_0.tar.gz "boost 1.58.0")
