Merge branch 'release/2.3.8' into develop
added design documentation
trying a different travis config
adding travis_retry during install travis config
added ignore raise NotImplementedError
added links to requires.io
clean up to further simplify implementation of pid lockfile
converted from previous use of 1 or 0 to represent True and False when setting values to be stored in the database
replaced empty abstract methods with raise NotImplementedError for clarity and coverage
skip adding files found with the torrent if not found on filesystem to avoid processing a torrent w/o files to process; general cleanup and simplification of code
code cleanup and simplification and duplication
added logic to stop workflow from continuing execution when a task associated with a media file failed to further support retry
update ChangeLog based on recent changes
added more test cases
fixed minor pep8 issues within new test cases
Update to version v2.3.9
Merge branch 'release/2.3.9'