first opinion on rust: pointers are hard.

or at least neither easy nor simple. but if something better than C++
with similar performance comes out, maybe it'll stay. or the
docs/tutorials get better, we'll see.

rust/README.md

# Rust
- when to use? lower level than go (no gc, very direct mapping to
    machine instructions), but still types and fun.
current status:
- i find it hard to get my head around all the pointer types, when to
    use them and why some things result in errors.