Improve pysox by adding `static-sox` package to auto download sox binaries

[zackees]

Hi there, great library.

I wanted to let you know I created a static-sox for tools like this so that the user doesn't have to face the pain of pre-installing sox for their platform in order to use the binary.

Consider adding static-sox to the dependency list and then using static_sox.add_paths(weak=True) in functions before they invoke a call to the sox binary.

static-sox will only download the binaries on first use, and there is a file based lock that will make sure the downloading step is only done once even in a concurrent environment.

pip install static-sox
https://pypi.org/project/static-sox/