- Reorder README to have implementation list after "learning tool"
bullet.
- This also moves tests/ and libs/ into impls. It would be preferrable
to have these directories at the top level. However, this causes
difficulties with the wasm implementations which need pre-open
directories and have trouble with paths starting with "../../". So
in lieu of that, symlink those directories to the top-level.
- Move the run_argv_test.sh script into the tests directory for
general hygiene.
