Async & Mac Build

This week, I implemented todos in the async code. There was plenty to do, but I managed to find some time to fix build errors on mac after ignoring them for so long. All the SIMD code works on mac as well, minus one incomplete and untested function. I took a look at kqueue for watching folders. It not reporting which file in the folder was modified is pretty annoying. I didn't write the code to detect what changed since there's higher priority things to do.