Changes: This is a bugfix release. (#36)
- Bugfix: gt and lt implemented but missing ge and le in Header.
- Bugfix: Attributes.remove() method would fail to remove properly if with_value is None and index is not provided.
- Bugfix: Support negative index in Attributes.insert() method.
- Bugfix: Delete an attribute no longer remove members that are named after the target key. #35
- Improvement: Docstring additions.