Profile code, benchmark

It would be helpful to know what mailhandler 2.x is capable of in terms of fetch/parse/process n. messages per minute, and what some of the slow points are. This could be compared to regular feeds node processing. It would be important to account for network latency, by either tracking the time that goes toward fetching where internet connection / imap stream occurs, or, fetching from a mailbox on the same machine as where mailhandler is running.