The changes on master Rust insert debug sections now (yay!) but this means that
wasm binaries by default pick up debug sections from the standard library, so
let's remove them by default in wasm-bindgen unless `--debug` is passed
Currently errors are reported via Rust panics but there's lots more errors being
added over time so this commit starts the movement towards the `failure` crate
to more idiomatically report errors as well as provide better error messages
over time.
