Turns out there was a bug when passing a vector of `JsValue` instances back to
JS all objects were leaked rather than correctly removed from the global slab.
This commit adds support for both `#![no_std]` in the wasm-bindgen runtime
support (disabled by default with an on-by-default `std` feature). This also
adds support to work and compile in the context of `#![no_std]` crates.
Closes#146
Nowadays the compile times are mitigated with incremental compilation and
otherwise it's much more ergonomic to run only one test if they're all in the
same suite.
