Comment 8 for bug 706774

Even in case of comment #2, aptitude is not needed to purge packages at least in Ubuntu 14.04, when using ppa-purge - 0.2.8+bzr63. Consequently, I think aptitude is not needed as an alternative in the script. ppa-purge (0.2.8+bzr63) still seems to have aptitude potentially used e.g. in case `apt-get install` fails which may happen, if user answers 'n' to apt-get's prompt!