find_last_by_* dynamic finder

I think you forgot to remove the old implementation of determine_finder().

I'm not sure if find_first_by is a good addition though because one would need to decide between using find_by and find_first_by and in this case a choice creates confusion (ie. do you use 'first_by' because it is more explicit and communicates the meaning of the code better of 'by' because it's shorter, easier to read/write).

Thanks for the comment. Attached new patch.

Automatic cleanup of spam.