add plucking of multiple columns to rails 3, taken from http://meltingice.net/2013/06/11/pluck-multiple-columns-rails/
add plucking of multiple columns to rails 3, taken from http://meltingice.net/2013/06/11/pluck-multiple-columns-rails/

unipept/unipept,unipept/unipept,bmesuere/uni-test,unipept/unipept,bmesuere/uni-test,unipept/unipept,unipept/unipept,bmesuere/uni-test,bmesuere/uni-test,bmesuere/uni-test