v0.3.0
* Basic encoding support added in `Encoding` and `EncodingSupport`.
* Internal remapping/removal of `util` from `binding` and `rubysys`.
* Various memory optimizations reducing heap allocation.
* Refactoring a few `rubysys` internal flags and re-implement `is_frozen` to be
completely in Rust.
* TryConvert added for implicit Ruby conversions to return either the type or nil.
