Some adjustments in setup scripts and Vagrant version

Hi,

I created a pull request (here in https://github.com/fastai/courses/pull/180) to address an issue with the recreation of all security group, VPC, Internet gateway, subnet, and route table whenever I run the setup_p2.sh multiple times without running the fast-ai-remove.sh (pretty much because sometimes I forget that I’ve ran the setup script). I also update the images in setup_p2.sh to reflect what @jeremy posted.

In addition, I created a version that mixes shell scripts, that creates all the infrastructure, and Vagrant, that creates the EC2 instance with Elastic IP set. In this version, I can destroy EC2 instance and recreate it without having to access the AWS console and I can execute commands after the instance is up. The repository is here: https://github.com/andretadeu/vagrant-fastai.

I did this for my own convenience, however if anybody find it useful, fell free to use it.