From%20the%20fun%20of%20a%20first%20riding%20lesson%20to%20the%20drama%20of%20a%20dressage%20competition%2C%20this%20entertaining%20activity%20book%20will%20keep%20young%20horse-%20and%20pony-lovers%20busy%20for%20hours%20on%20end.%20With%20over%20250%20stickers%20of%20horses%2C%20riders%2C%20equipment%2C%20trophies%20and%20more.