Add support for several /sys/class/sas_* classes (#453)

* Initial addition of several sysfs/class_sas* files, plus fixtures.

These parse several SAS classes from /sys/class/
  - sas_host
  - sas_device
  - sas_end_device
  - sas_expander
  - sas_port
  - sas_phy

The included fixtures include examples of all of these.

Signed-off-by: Scott Laird <scott@sigkill.org>

Author: scottlaird