Add block to Mapper#find
Add Mapper#reject method

Only works for equality
Refactor Mapper#select to match Mapper#reject
Prefer public_send over send
Add reject functionality to comparison functions
Add reject functionality to regexes
Alias mapper#detect to mapper#find
Alias mapper#find_all to mapper#select
Add block functionality to Mapper#count
Compare actual results
Allow count to take criteria as arg or block