* Introduce and document the `url` feature
* Implement `From<&GeoUri>` and `From<GeoUri>` for `Url`
* Implement `TryFrom<&Url>` and `TryFrom<Url>` for `GeoUri`
* Add and extend tests
* Don't set the `homepage` field in `Cargo.toml` if it is the same as
the repository (C-METADATA)
* Don't use `expect` but `?` in examples (C-QUESTION-MARK)
(This cannot be fixed for the README for now, unfortunately)
* Document the errors for all methods which return a `Result`
(C-FAILURE)