Merge pull request #548 from youyong205/master

add the document
amend rules' check range
fix HeartbeatAlert bug
Merge branch 'master' of https://github.com/dianping/cat
Merge pull request #549 from leonindy/master

fix HeartBeatAlert bug, amend rule configs check range
Merge branch 'master' of github.com:dianping/cat
modify the jsp