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.
Merge pull request #1 from charliesome/patch-1

Clean up JobWrappers::ResqueWrapper.perform