[TACHYON-127] WIP: Create Tachyon Cluster via Vagrant 

This obsoletes #452 

While it is still work-in-progress, feedback is badly needed for this work. 

What's working?
We can start a two-VM Tachyon cluster using HDFS 2.4.1 and glusterfs as under filesystem.

What next?
- more under filesystem (ceph, hadoop 1.0.4)
- more providers: Docker, OpenStack, AWS, VMWare Fusion.

@haoyuan @childsb @uronce-cc @dcapwell @hsaputra 
Could we be generating RSA keys instead of checking these in? I see this being a potential security issue.