Creates option to define queue in enqueue form.

[GMolini]

• Ive added an option in the enqueue form so that the user can specify there in which queue he wants to enqueue the job. By default, the gem will use the deduce_queue method to automatically populate it, so if the user has defined it in the job it will already have that value.
• Ive also added a check to only add jobs to the job list when they have a perform method defined. It was throwing me an error because I hade a "Base" worker without a defined perform method that would be defined by the child classes. Let me know what you think of this changes