Switch from VM based travis-ci to container based

[bastelfreak]

VM shit runs on ubuntu 12.04, container on 14.04 but they do not have sudo. But there is a apt provider to install certain packages:

---
sudo: false
language: python
python:
  - "3.3"
addons:
  apt:
    packages:
      - libvirt-bin
      - python-libvirt
install:
  - pip install tox
script: tox -e testxunit
env:
  global:
    - DEBIAN_FRONTEND=noninteractive
    - PACKAGE=python-libvirt
  matrix:
    - TOXENV=py33
    - TOXENV=py34
    - TOXENV=py35
    - TOXENV=pypy3
notifications:
  irc:
    on_success: change
    on_failure: always
    channels:
      - "irc.freenode.org#virtapi"
  email: false

the needed packages are not approved yet:
travis-ci/apt-package-safelist#723
travis-ci/apt-package-safelist#2385

we can migrate when these issues are resolved