Adding "args" method to AnyEvent::Beanstalk::Job

Hey!

According to the docs, $job->args should return the decoded job data. That matches Beanstalk::Client::Job. But when I looked at the code, the method was actually $job->decode.

I've modified AnyEvent::Beanstalk::Job to make those two methods synonyms, added some quick tests to 01-simple.t, and since I was looking at the unit tests anyway I made "start_server.pl" a package, added warnings tests, some test names, &c.

Let me know if there's anything you'd like me to change.

Cheers!