Adds a rake command to read web server log files from a rails app layer instance

Also changes --session-command to -c for compatibility with Ubuntu. It does not break CentOs based servers, according to these two man pages:

su on CentOS : http://grisha.biz/cgi-bin/man?query=su&apropos=0&sektion=0&manpath=CentOS+release+5.3+%28Final%29&format=html
su on Ubuntu/Debian : http://manpages.ubuntu.com/manpages/precise/man1/su.1.html

Also see this discussion : http://askubuntu.com/questions/405568/why-cant-i-use-su-session-command-on-ubuntu