added Postgresql example Dockerfile of CentOS
added pyhton and vim gitignore
implemented new checks, src in general needs refactoring
added return code to __main__
Merge branch 'master' of https://github.com/goern/dockerfile_checker
moved TODO to README
moved the dockerfile examples around
added a link to the upstream project
removed reference to RH internal document
added GPL text@
implemented check if some ports got exposed