Added stdin option for SnapshotLoader.
Added stdin option for SnapshotLoader.

SnapshotLoader now is able to be configured to take input from stdin.

jdellithorpe/RAMCloudUtils,jdellithorpe/RAMCloudTools,jdellithorpe/RAMCloudUtils,ellitron/RAMCloudTools,ellitron/RAMCloudTools,ellitron/RAMCloudTools,jdellithorpe/RAMCloudTools,jdellithorpe/RAMCloudUtils