Add first-pass Vagrant support

This changeset provides a Vagrant development environment for running
Spark within a Mesos cluster. The cluster includes the following
services:

- HDFS (CDH 5)
- Zookeeper (for Mesos leader election, CDH 5)
- Mesos
- Marathon
- Spark (CDH 5)
- libgdal-java

See `README` for more details.