Use newer version of ubuntu in vagrant. Extended LTS

[cal-pratt]

This PR fixes half of issue #272 We still need to re-install ubuntu on the topside computer to use the same ubuntu version.

The ubuntu version wily reached its end of life shortly after the competition last year and was recently removed from the ubuntu cloud images. I guess this was to promote companies (like ourselves) who are using non-supported software to change to supported versions. I chose to upgrade to ubuntu xenial as it's the latest version on ubuntu marked as LTS (long term support).

Some caveats to mention about this change:

• This update did not work on out of date VirtualBox/ vagrant versions. I recommend updating to the latest versions of both programs (On windows I'm on VirtualBox 5.1.14 and Vagrant 1.9.1). Also delete the entirety of your ~/.vagrant.d/ directory.
• In vagrant the xenial default user appears to be ubuntu, and the default password is not provided for security reasons. Because of this I added a provision shell command to forcefully change this password to eedge, which is nice because now all of passwords are consistent across the board.
• The squid3 program now defaults to just squid, so I had to update the captain playbook. So use squid instead of squid3!

Apart from that it all looks hunkydory; gradle builds with no errors. @ConnorWhalen give this a shot on your mac to make sure it's all good on your end. 🤞