Added missing reference to sha256.rb to .gemspec
Added missing reference to sha256.rb to .gemspec

lukeasrodgers/authlogic,nedforce/authlogic,nebulab/authlogic,janusnic/authlogic,nulogy/authlogic,rchekaluk/authlogic,sideci-sample/sideci-sample-authlogic,awd/authlogic,fanda/authlogic,brandonbloom/authlogic,bioritmo/authlogic,theiren46/authlogic,manvil/authlogic,binarylogic/authlogic,tiegz/authlogic,Photovisi/authlogic,jaredbeck/authlogic,taf2/authlogic,bryanl/authlogic,boone/authlogic,antonifs/authlogic,expertiza/authlogic