MADRID, Feb 7 (Reuters) - World Player of the Year Lionel Messi has signed a new contract with Barcelona which ties him until June 30 2018, the Spanish league leaders said on Thursday. The 25-year-old penned a deal agreed in December, which includes a two-year extension on his previous agreement and secures his services until he is 31. The Argentina captain joined Barcelona's youth academy as a 13-year-old and made his first-team debut at 16. ... More...