Merge pull request #12 from beppu/master

add instructions for etc/log.conf
context sensitivity to debian/ubuntu version

This should alleviate some of the infinite looping mentioned in #10.
Percona should install successfully.  Let me know if it doesn't.
I tested it on Ubuntu 14.04 LTS (trusty).
install libpng-dev
a comment about DEBIAN_FRONTEND=noninteractive