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