While much of the U.S. and the markets enjoyed a post-holiday break on Monday, President-elect Donald J. Trump used his favorite means of communication, Twitter, to take credit for the stock market bounce and holiday sales and to wag his finger at the United Nations and President Barack Obama. In a tweet, Trump claimed “there was no hope” before he won the election in November, and that now the market has jumped 10% and Christmas spending is over $1 trillion.