Log stderr and stdout to file

Depends on #32 
Similar to https://github.com/cargomedia/socket-redis/blob/master/lib/utils.js#L15

Add some debug logging.
@njam @kris-lab What do you think about this style of logging when `log.debug` replicate message of `log.info` with addition of debug data? Isn't that excessive info? Would not it be better to just use `log.debug(params, task)`? I've done the replication of messages because logging is async and in the end actual log messages can occur on different lines in log file. The probability of this is low but still it exists.