Rake trace

Some of the recent Travis CI builds had been failing. I'm unsure of exactly what caused this, but upgrading the version of Foodcritic seemed to have fixed them in Travis CI build 47. (https://travis-ci.org/rtkwlf/cookbook-simple-iptables/builds/20792760) The --trace option is now used with rake to try and get more information from it if something goes wrong in the future.