This year’s Martin Luther King Jr. Symposium at Tufts University will focus on the theme of “Cashing Our Promissory Note: Race, Justice, and Reparation,” based on the powerful quotation from  King's speech at the March on Washington in 1963. Author, historian and journalist Jelani Cobb will give the keynote address. Cobb is the Ira A. Lipman Professor of Journalism at Columbia University as well as staff writer for The New Yorker, where he writes about race, politics and injustice. He…