IHEX 3.0: 2018 Edition
- Moved to Rust 2018 edition.
- Applied all suggested lints from clippy.
- Applied all suggested formatting changes from cargo fmt.
- Removed conflicting implementation of Record::to_string (should-out to @skrapi)
- Flattened the top-level module namespace.
- Various tweaks and performance enhancements.
NOTE: The changes from Record::to_string into to_record_string, the addition of ReaderOptions and some minor error constant tweaks and module structure is a breaking source-level change, necessitating bumping the major revision.