The Luna aims to challenge the dominant Hass, but probably not for a few years
                                
                                
                                    (Newser) -
                                    Look out, Hass, there's a new contender for the guacamole throne. It's the easier-to-harvest Luna, developed, according to  Axios , over the course of 50 years at the University of California-Riverside. The university announced the Luna in a  release , though it will probably be at least three years before...