add backtrace feature for splat matching

[dzyhenry]

Add backtrace feature for splat matching to support case like follows:

    // when route set like follows
    hash.set('/a/b/c', routeHandlerABC);
    hash.set('/a/b/*', routeHandlerABStar);
   
  // /a/b/c/d could match /a/b/*
   var res = hash.get('/a/b/c/d');
   assert.strictEqual(res.handler, routeHandlerABStar);