Prime Movers: The Makers of Modern Dance in America. By Joseph H. Mazo. Illustrated, 322 pp. New York: William Morrow and Company, Inc., 1977. $12.50. Lester Horton: Modern Dance Pioneer. By Larry Warren. Illustrated, 265 pp. New York: Marcel Dekker, Inc. $12.75. Soaring: The Diary and Letters of a Denishawn Dancer in the Far East, 1925–1926. By Jane Sherman. Illustrated, 278 pp. Middletown, Connecticut: Wesleyan University Press, 1976. $14.95.