v0.3.0

For use with dcos-vagrant-box v0.3.0

Changes:

• Sped up box download by ~2x by moving the catalog and box files from vagrant-cloud to S3 (downloads.mesosphere.com/dcos-vagrant)
• Extracted the box builder to https://github.com/mesosphere/dcos-vagrant-box
• Worked around a certificate authority bug (DCOS is compiled on ubuntu and centos has certificates in a different place) to fix Cassandra and Kafka
• Added early validation for required files
• Exposed failure output of dcos_install.sh execution to aid debugging
• Added an oinker on kubernetes example: https://github.com/mesosphere/dcos-vagrant/tree/master/examples/kube-oinker