Add a metricType into CatConstants
Merge pull request #146 from ainilife/biz-abtest

Refactor the abtest code.
Merge branch 'biz' of https://github.com/dianping/cat into biz-abtest
Add unit test for WaterfalMessageCodec.java
Refactor WaterfallMessageCodec
Remove require restrict for url input in the abtestCreate.jsp
Add unit test for TcpSocketReceiver.java