The engaging and surprising crime film “Reptile” is flying slightly under the radar and perhaps even somewhat underestimated. Maybe it is because it’s a Netflix film, which often falls into—one piece of content of many, for better or worse—maybe it’s because it’s been marketed in a pretty standard straightforward way that makes it look like a prototypical crime or killer procedural (hey, they have to sell these things in the simplest ways they can).