Use case/when

Implemented delayed_job support

Dont need the explicit error handling -- if the require fails, it will raise exactly the error we want to communicate anyway. Also use the load path, so we can allow plugins, rather than requre_relative

Lazy-load adapters, fixes #6

 Add Sidekiq adapter/wrapper fixes #3

Clean up JobWrappers::ResqueWrapper.perform

This is not only easier to read, but it'll also properly raise an ArgumentError rather than a NoMethodError when called with no arguments.

It also allocates 4 fewer objects per call (8 down from 12), and is about 50% faster according to a quick benchmark.

Queue naming with a base, which requires a JobWrapper to comply to Resques expectation of a class variable