Fix logging madness

- Log lymph.ping request as debug
- Workaround gevent to log http requests using python logging (https://github.com/gevent/gevent/issues/106)
I'd rather remove it then. If gevent somehow manages to write to the buffer we just leak memory, and if it was to use seek()/tell() the log output would be broken. We should see these cases as errors in our logs and fix them.