avocado.utils.archive: Add support for .tar.xz [V3]

ISSUE: https://github.com/avocado-framework/avocado/issues/80

This patch wraps LZMA archive in order to work with python 2.7 tarfile.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>

Changes V2

* sorted out Travis CI dependencies

Changes V3

* rpm/deb dependencies