Support a :on argument to predictions_for to return only scores for specific items.
Merge pull request #19 from Pathgather/scores-on

Support a :on argument to predictions_for to return only scores for specific items.
make respond_to compatible with Ruby 2.x
Merge pull request #22 from hakunin/support/respond-to-ruby-v2.0-compatible

make respond_to compatible with Ruby 2.x
Merge branch 'master' into performance

Conflicts:
	spec/base_spec.rb