Gearman README formatting, word wrap
Start an independent, PostgreSQL-backed instance of Gearman on "localhost:4731"
Add initial Gearman-based extractor module:

* Add MediaWords::DBI::Downloads::extract_and_vector() subroutine with self-contained "extract or store the error in database" code
* Add MediaWords::GearmanFunction::ExtractAndVector Gearman worker to be used for local and Gearman-based extractions
* Move "mediawords_extract_and_vector.pl" to "mediawords_extract_and_vector_locally.pl" to specify what the script is doing
* Add "mediawords_enqueue_unextracted_downloads_on_gearman.pl" helper script
Merge branch 'master' into gearman_extractor
Require Gearman::JobScheduler 0.12 which supports unify_logs()
Write a single Gearman extractor log because there are a lot of extraction jobs so it's impractical to log each job into a separate file
Require Gearman::JobScheduler 0.13 which sanitizes function names in log paths properly
Merge branch 'master' into gearman_extractor
Enqueue extraction job on Gearman after each 'content' download
Require Gearman::JobScheduler 0.14 which doesn't use (broken) forks anymore and stores Gearman job arguments in JSON
Update documentation according to the new extractor infrastructure
In Gearman workers, connect to the PostgreSQL database only once in the package because Gearman::JobScheduler no longer is designed to support fork()s so this should be thread-safe (as there are no threads)