upgraded dependence of resque to support 1.25

1. the 1.25 version removed 'require resque/helper' , so the "Resque.constantize(klass_name)" don't work anymore. I fixed this by adding our own helper methods.
2. why we don't upgrade 'yajl-ruby' to 1.1.0 ? (0.8.2 got problem with Mountain Lion.)
3. All tests passed on ruby 2.0 .
4. Thanks.