Update the Vagrant box

Most notable changes are:

• Set swap only when virtualbox is used as the provider
• Set up GDK in the vagrant box after installation
• Update base docker image to xenial (16.04)
• Install yarn in the box

Other minor updates:

• Update ruby version to 2.3.3
• Use nodejs 6.x from a PPA
• Suppress runlevel warnings
• Specify noninteractive installs

Resolves #258 (closed), #188 (closed)