I’ve been reading about cats,” my husband, Peter, tells me. Peter has never had a cat before. “Oh, yeah?” “Salt is not good for their kidneys. We have to give Felix unsalted fish.”Felix is our adopted street cat here in Mexico. He is coming back to the U.S. with us in a fancy backpack carrier I found online. It has mesh on either side, with one big plexiglass bubble in the back, so Felix can watch his fellow passengers in comfort. He hasn’t flown yet, but our trips to and from the veterinarian were uneventful, so I think he will ...