add support for estimate target site other than baidu

change the err log for http error requested part to debug

I do this since someone see baidu in our company traffic log and ask for the reason, since it was in top of that traffic. 
Baidu is not used here, and also its not fast here too. so I need an option to change this to another address. 

ps - I use emacs hook on save so goimports change the imports order too. I think its a good idea to fix all this files using goimports , but if you want, I can revert that part.