update README.md

Author: shi-yuan

README.md

@@ -20,8 +20,18 @@
 | 5.0.0         |     5.0.0     |
 | 5.0.1         |     5.0.1     |
 | 5.0.2         |     5.0.2     |
-| master        |     5.1.1     |
+| 5.1.1         |     5.1.1     |
+| master        |     5.1.2     |
 
+##5.1.2 插件安装
+
+进入Elasticsearch目录运行如下命令
+
+````
+进入es目录执行如下命令
+
+./bin/elasticsearch-plugin install https://github.com/NLPchina/elasticsearch-analysis-ansj/releases/download/5.1.2.0/elasticsearch-analysis-ansj-5.1.2.0-release.zip
+````
 
 ##5.1.1 插件安装