rails dup behaviour changed

deep_dup not returning object references in a way that delayed_job could handle them correctly (failed during yaml conversion)

before fix:
![screen shot 2014-07-21 at 12 21 07](https://cloud.githubusercontent.com/assets/1729955/3642801/fd168f30-10c7-11e4-9fcf-c0e49e749f09.png)

after fix:
![screen shot 2014-07-21 at 12 20 58](https://cloud.githubusercontent.com/assets/1729955/3642803/06682fee-10c8-11e4-98e0-9c0df94abe05.png)