Bad news for Uber: Didi Kuaidi, China’s top ride-sharing service, has joined forces with Lyft and invested $100 million in the company. Less than a day after Chinese ride-hailing giant Didi Kuaidi made public a $100 million investment in Lyft, the two companies held a press conference announcing a “two countries, one app” solution as well as mutual technological and financial cooperation. Didi Kuaidi has proven to be a formidable opponent for Uber, which has…