Rename VagrantFile to Vagrantfile

Despite https://docs.vagrantup.com/v2/vagrantfile/ stating that "casing doesn't matter", the issue at https://github.com/hellais/TAILS-OSX/issues/50 suggests otherwise. I also reproduced this by using a case sensitive formatted disk image and was able to test the fix this way.

I also created an issue on the vagrant github for this bug too: https://github.com/mitchellh/vagrant/issues/4907
Changed links to Tails v1.2.1 ISO and signature

1.2 was no longer available for download.

Changed links to get v1.2.1
Added MacBook Pro 8,1

Added MacBook Pro 8,1 from https://github.com/hellais/TAILS-OSX/issues/50
Improved cleaning data directory

Previously .gitignore would have been deleted, and the files were temporarily moved which was not ideal.

Now nothing is moved and everything in the data folder except the BOOTX64.efi and .gitignore file are deleted.
Merge pull request #52 from Grezzo/master

Updated to 1.2.1 and dealt with issue 50