work in progress on #69
Merge branch 'master' of github.com:duke-libraries/dul-hydra
closes #69
closes #70
add tests for failre validation preservation events
closes #71
added comments; replaced ds_internal_uri module method with instance method
Moved ds_internal_uri to instance method of DulHydra::Models::HasPreservationEvents
added #ds_internal_uri; removed #last_fixity_check (use fixity_checks.last); fixed oversight in ::find_by_last_fixity_check; added before_destroy callback and protected method
Updated spec tests for recent changes