Merge pull request #36 from pwendell/v2

V2
update to use tachyon 0.4.0
use s3 to download tachyon jar
Merge remote-tracking branch 'upstream/v2' into v2
Merge pull request #39 from haoyuan/v2

Upgrade Tachyon to v0.4.0
Initial support for XFS
Brute-force approach to mounting xfs drives.

This just assumes the ext3 drives are already set-up and re-mounts
then as XFS if they are empty.
Find mounted devices and not EBS ones.