Update to embedded-hal v1.0

[wowkster]

At this point embedded-hal v1.0 has been out for several months now. Is there a good reason to stay on embedded-hal v0.2.4 for this crate? If not, upgrading should be considered in the near future.

[eivindbergem]

The serial::Read and serial::Write traits have been removed from embedded-hal v1.0 and the crate already implements Read and Write from embedded-io, so in a way it supports both v0.2.4 and v1.0.0.