feat(image_to_vm): Add new and improved qemu wrapper script.

This one is more automagical and sets up ssh keys from ssh-agent and the
user's home directory by default. Also adds an option for setting the
ssh port so it can be something other than 2222. Script should be
sufficiently portable, tested in bash, dash, and ash.
Merge pull request #89 from marineam/qemu

feat(image_to_vm): Add new and improved qemu wrapper script.