Rq-scheduler

* Support for RQ 2.0. Thanks selwin!

* Support for RQ 1.14. Thanks HerrTxbias!
* Added `result_ttl` and `ttl` arguments to `scheduler.cron()`. Thanks marcelblijleven!

* Minimum Python version is now 3.6. Thanks ronlut!
* Support for RQ 1.13. Thanks ronlut!
* Added `at_front` parameter to `enqueue_at()`. Thanks gabriels1234!
* Added support for `on_success` and `on_failure` handler to `enqueue_*` methods. Thanks andy-takker!
* Replace `croniter` with `crontab` package. Thanks zentist!

* `Scheduler` now accepts `queue_class` argument. Thanks gisce!
* Fixes local timezone handling. Thanks Eugeny!

* You can now run multiple schedulers at the same time. Thanks oxalorg!
* You can now schedule a job with dependency by specifying the `depends_on` kwarg. Thanks noncomputable!
* Added `use_local_timezone` argument to `scheduler.cron()`. Thanks Eugeny!

* `scheduler._create_job()` now respects `queue_name` parameter. Thanks shubhamdipt!
* Added `queue_name` parameter to `enqueue_at()` and `enqueue_in()`. Thanks gauravmk!