fixed this import statement
debfile.DebFile is an internal interface only, so switched that for debpackage.DebPackage
simplified and cleaned up some
added lots of stuff for nicer pretty printing, cleaned up memory use somewhat
added modestr, to print a visual representation of permissions similar to the output of `dpkg --contents`
initial stub
added first tests for ArFile and DebFile
added __pycache__ to .gitignore; enabled actual testing in .travis.yml; added pytest to requirements-test; updated tox.ini