Merge pull request #71 from ainilife/master

Refactor the code
Merge branch 'master' of github.com:dianping/cat into abtest
Merge pull request #74 from unidal/abtest

Promote ABTest features from abtest to master
fix merge issues
Merge pull request #75 from unidal/abtest

fix merge issues
revise cat api
abtest code wrapup for further test
Merge pull request #79 from unidal/abtest

for further integration test
ABTest bug fix.