By Martyn Herman ALCUDIA, Mallorca, Jan 12 (Reuters) - Tour de France champion Chris Froome has extended his contract with Team Sky until 2018, the British outfit said on Tuesday at their pre-season training camp in Mallorca. Team leader Froome, 30, won the Tour de France with Sky in 2013 having helped team mate Bradley Wiggins to victory the year before. "Chris is not only one of the most talented and dedicated riders in the world, he is also a fantastic ambassador for the sport," Team Sky boss Dave Brailsford said of the Kenyan-born Briton who joined Sky in 2010. More...