Unsupported!() macro for compile errors when a code path is used

crates.io: Rust Package Registry (my entry to the worst crate name competition ;)) It implements compile-time errors when unsupported code paths are actually taken. This helps to get rid of runtime panics from using todo!() or unimplemented!(). It also allows a novel programing pattern allowing traits with optional methods that the user only needs to implement when they are actually used. It is a very small crate, I was honestly surprised such didn't already exist, still I believe it was wor...