- Update to support axum 0.2
  [#303](https://github.com/lambda-fairy/maud/pull/303)
- Add support for `Option<T>` attributes using the `attr=[value]` syntax.
  [#306](https://github.com/lambda-fairy/maud/pull/306)
- Update to Rust 2021
  [#309](https://github.com/lambda-fairy/maud/pull/309)
- Remove Iron support
  [#289](https://github.com/lambda-fairy/maud/pull/289)
- Disallow slashes (`/`) in void elements
  [#315](https://github.com/lambda-fairy/maud/pull/315)