WASHINGTON — Comedian Dave Chappelle has been chosen to receive this year's Mark Twain Prize for American Humor.The 45-year-old Chappelle shot to international stardom through his Comedy Central program, "Chappelle's Show," which gleefully skewered racial stereotypes and hot-button societal issues. He later made headlines for walking away from a lucrative contract over creative differences.Chappelle attended Washington's Duke Ellington School of the Arts, [...]