降低servlet版本号为3.0，以支持tomcat7

Author: binarywang

src/main/webapp/WEB-INF/web.xml

@@ -1,8 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
- xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
- version="3.1">
+ xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_0.xsd"
+ version="3.0">
  <!-- Spring -->
  <!-- 配置Spring配置文件路径 -->
  <context-param>