added support for logfile-per-domain environments#18

Hosting environments often tend to use an individual log file for each domain. As the domain name isn't included in the URL, the name of the log file is the only clue on which domain a request was served for. In conjunction with the following command, a large number of log files can be handled by apachetop and the names of the log files can be shown to the user. `ls -t /var/log/apache2/logs/*.log | head -n 2000 | sed -e 's/^/-f /' | xargs -o apachetop`