Feature/natea/aws provider

Rather than touching the existing Vagrantfile, I chose to make a new Vagrantfile-aws. You may want to incorporate these changes into the existing Vagrantfile, so there's only one file to maintain.

Similarly, there is a special provision-aws.sh script which differs from provision.sh, but could probably be incorporated into provision.sh, so there's only one file to maintain. The provision-aws.sh script borrowed from Dockerfile, so as to match the conventions used there.

The README explains a few other steps to get things working smoothly on AWS.