Boston Ballet has picked up two big-deal dancers from the ballet company of La Scala in Milan. Petra Conti and Eris Nezha , who are newly married, will join the troupe as principal dancers in October. Boston Ballet principal dancers Lorna Feijoo and Nelson Madrigal also joined as a couple.Mark Shanahan can be reached at firstname.lastname@example.org. Follow him on Twitter @MarkAShanahan. Meredith Goldstein can be reached at email@example.com. Follow her on Twitter @MeredithGoldste.