by John BIERS Agence France Presse NEW YORK, United States (AFP) — Tesla Motors overtook General Motors to become the biggest US automaker by market capitalization Monday, a sign of how Silicon Valley has captured investor excitement at Detroit’s expense. Tesla shares were up 3.0 percent to $311.74 near 1720 GMT, for a market capitalization of $51.43 billion, more than $1 billion above GM, a 109-year-old company that sold almost 120 times as many cars […]