net/http

I will graduate httpclient because I met difficulties to finish threads properly in multi thread environment (related with https://github.com/yohoushi/fluent-plugin-yohoushi/pull/6)

Maybe this is caused by the timeout treatment of httpclient. See https://gist.github.com/sonots/8780628. httpclient uses `timeout` method, wheres `net/http` is taking care of it using nonblock and IO.select https://gist.github.com/sonots/8784780. `net/http` is proper.