update storage-pool name rules

-support multi-user usage on host
 +fixed #191

-support box version that is introduced in vagrant 1.5+
 +fixed #190

Signed-off-by: Hiroshi Miura <miurahr@linux.com>
use userid not username for spool suffix

Signed-off-by: Hiroshi Miura <miurahr@linux.com>
Merge pull request #237 from miurahr/issue191

fix spool problems