Replace auto_now_add with a custom signal. Fix bug 747887.
Replace auto_now_add with a custom signal. Fix bug 747887.

flamingspaz/remo,abdullah2891/remo,chirilo/remo,Mte90/remo,akatsoulas/remo,johngian/remo,johngian/remo,mozilla/remo,johngian/remo,akatsoulas/remo,abdullah2891/remo,tsmrachel/remo,abdullah2891/remo,chirilo/remo,johngian/remo,Mte90/remo,akatsoulas/remo,Mte90/remo,flamingspaz/remo,flamingspaz/remo,mozilla/remo,mozilla/remo,tsmrachel/remo,chirilo/remo,mozilla/remo,Mte90/remo,tsmrachel/remo,chirilo/remo,akatsoulas/remo,abdullah2891/remo,flamingspaz/remo,tsmrachel/remo