README.md in unidom-common-1.8 vs README.md in unidom-common-1.8.1

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 # Unidom Common 常用领域模型引擎
 
+[![Documentation](http://img.shields.io/badge/docs-rdoc.info-blue.svg)](http://www.rubydoc.info/gems/unidom-common/frames)
 [![License](https://img.shields.io/badge/license-MIT-green.svg)](http://opensource.org/licenses/MIT)
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 [![Gem Version](https://badge.fury.io/rb/unidom-common.svg)](https://badge.fury.io/rb/unidom-common)
 [![Dependency Status](https://gemnasium.com/badges/github.com/topbitdu/unidom-common.svg)](https://gemnasium.com/github.com/topbitdu/unidom-common)
 
 Unidom (UNIfied Domain Object Model) is a series of domain model engines. The Common domain model engine includes the common models.
 Unidom (统一领域对象模型)是一系列的领域模型引擎。常用领域模型引擎包括一些常用的模型。