Make javascript and glsl Minkowski signature consistent

[roice3]

This is just to remind us about this code cleanup need.

It's +++- in the javascript, and ---+ in the glsl

(slightly related: it's a bummer that I had to add a separate lorentzDot method for the three.js vector structure. I wonder if there might be a way to avoid that.)

[mtwoodard]

Should be fixed now.