Merge pull request #317 from jialinsun/master

添加异常告警选项自动添加Dfault和Total选项，修改网络和异常文档
添加异常过滤配置，修改exception alert规则和alert report build规则，添加异常过滤文档说明，修改topreport visitor test case
Merge branch 'master' of https://github.com/dianping/cat