A man sentenced to life in prison without parole on a marijuana-related charge was freed Tuesday from a Missouri prison after being behind bars for two decades — a period in which the nation’s attitudes toward pot have steadily softened. Family, friends, supporters and reporters flocked to meet Jeff Mizanskey as he stepped out of the Jefferson City Correctional Center into a sunny morning, wearing a new pair of white tennis shoes and a shirt that read “I’m Jeff & I’m free.”