[Review] Request from 'aduffeck' @ 'SUSE/machinery/review_141120_filter_special_mounts_when_inspecting_unmanaged_files'

Please review the following changes:
  * 088ac22 Filter special mounts when inspecting unmanaged files,e.g. procfs mounts
  * ed4bf05 Add MountPoints#special which returns a list of special mounts like proc
  * 345401a Merge pull request #383 from SUSE/review_141114_warn_when_comparing_extracted_with_unextracted_unmanaged_files
  * 93aecff Add test for warning when comparing unextracted with extracted files
  * 9334195 Show a warning when comparing extracted with unextracted unmanaged files