Document options when using "--provider=docker"

Signed-off-by: Gianpaolo Macario <gmacario@gmail.com>
.gitignore: Add phusion.key
Add support for Vagrant Docker provider

Signed-off-by: Gianpaolo Macario <gmacario@gmail.com>
Install package weget

Signed-off-by: Gianpaolo Macario <gmacario@gmail.com>
Adaptations to run as root

Signed-off-by: Gianpaolo Macario <gmacario@gmail.com>
Make --provider=docker more explicit

Signed-off-by: Gianpaolo Macario <gmacario@gmail.com>
Merge pull request #10 from gmacario/add-docker-provider

Add support for Docker provider to Vagrant