Implement TryFrom<&str>

[ranfdev]

Currently the Url type has an automatic TryFrom implementation returning core::convert::Infallible.

It would be nice to have a TryFrom<&str> returning url::ParseError, so that programs can do

fn get<U: TryInto<Url>>(dest: U) -> Result<()> {
}

(TryInto<Url> should be auto-implemented once there is TryFrom<&str>)

[ranfdev]

Uff, sorry, I didn't search the github issues enough.
This was already solved in #569.

If you can't find the trait on docs.rs, it's because the version with the required changes hasn't been released yet.