After visiting their first Shake Shack on a trip to Las Vegas last year, Brighton’s Rash family salivated at the thought of the New York City burger chain’s opening day in RiNo. So much so, in fact, that the family of four showed up at 8:45 a.m. on its opening day Wednesday, earning themselves the honor of being first in line for a taste of Colorado’s premiere Shake Shack — and even beating some employees there. “They told us, ‘You do realize we don’t open till 11, right?’ ” said Cherie Rash, 39. By the time 10:30 a.m.