Update fflib_SObjectUnitOfWork.cls

Added the ability to handle self-relationships, e.g. 

fflib_SObjectUnitOfWork uow = new fflib_SObjectUnitOfWork(new Schema.SObjectType[] { Account.SObjectType });             
Account parent = new Account(Name = 'Parent');
uow.registerNew(parent);
uow.registerNew(new Account(Name = 'Child'), Account.ParentId, parent);
uow.registerNew(new Account(Name = 'Child'), Account.ParentId, parent);
uow.commitWork();

Note: This is massively hack-y at the moment, but it works.