Tesla Motors CEO Elon Musk said Thursday night the electric automaker is beefing up its self-driving car software. The urgency of Musk’s offer, and the fact that he chose to tweet it to the public, could signal that the company is preparing to launch a self-driving mobility service akin to the one being built by Uber, the $51 billion ride-hailing service.  Tesla declined to comment on Thursday night about how many engineers it hopes to hire and its future plans for them. “We’re going to let the tweets speak for themselves,” a Tesla spokeswoman told The Huffington Post in an email.