Rust binding

[dhdaines]

Somebody already did this for PocketSphinx, though it needs to be updated: https://github.com/cmusphinx/pocketsphinx-rs

Evidently it will not be "batteries included" like the Python, as that is not very rusty.

This is a good stepping stone to rewriting the whole library in Rust, which is a good idea (though it will probably make it less smol, at least at first).