Fix database serialization of job class names with Que

When passing a class constant as a job argument, Que’s stored procedures serialize it to JSON in the database as `{}`. This means that when the job (the ActiveJob “wrapper”) is deserialized from the database, it can’t find the original job class to run again.

Changing the Que adapter to serialize the job class as a string fixes this behaviour. This change makes the adapter consistent with other adapters too (which constantize a class string in their JobWrapper#perform methods.
Merge pull request #100 from timriley/fix-que-class-serialization

Fix database serialization of job class names with Que
Rename variables for consistency.
Merge pull request #101 from DouweM/patch-9

Rename variables for consistency.
Update README.md
Improve the error message when resque-scheduler is not available
Fix the test requirement of resque_scheduler
Fixed qu, queue_classic, sneakers adapters
Merge pull request #103 from cristianbica/adapter-fixes

Fixed qu, queue_classic, sneakers adapters
Integration testing
Merge pull request #102 from cristianbica/integration_tests

Integration testing
Remove stray variable to fix the warning shown when resque-scheduler can't be loaded
Remove and ignore the dummy app's test sqlite database
Merge pull request #104 from packagethief/fix-resque-scheduler-load-warning

Remove stray variable to fix the warning shown when resque-scheduler can't be loaded
Merge pull request #105 from packagethief/ignore-test-sqlite-db

Remove and ignore the dummy app's test sqlite database
Revert "Remove and ignore the dummy app's test sqlite database"
Merge pull request #106 from rails/revert-105-ignore-test-sqlite-db

Revert "Remove and ignore the dummy app's test sqlite database"
Remove and ignore the dummy app's test sqlite database

Set the migrations path to our dummy app's db/migrate directory so
ActiveRecord::Migrator can find the last version, thus allowing the
test schema to be automatically be maintained.
Merge pull request #107 from packagethief/ignore-test-sqlite-db

Remove and ignore the dummy app's test sqlite database, take two
remove repeated sidekiq option