Merge branch 'release-0.6.0'

CHANGELOG.rst

docs/dev/environment.rst

docs/dev/quickstart.rst

docs/testers/howto.rst

pkg/linux/bitmask-root

pkg/linux/resolv-update

pkg/linux/update-resolv-conf

pkg/osx/Info.plist

pkg/osx/bitmask.icns

pkg/requirements.pip

pkg/tuf/init.py

pkg/tuf/release.py

relnotes.txt

setup.py

src/leap/bitmask/__init__.py

src/leap/bitmask/app.py

src/leap/bitmask/backend/api.py

src/leap/bitmask/backend/backend.py

src/leap/bitmask/backend/backend_proxy.py

src/leap/bitmask/backend/components.py