v0.4.0

This new version has some backwards incompatibilities you should be aware of. If successful, the crate will use it to hit v1.0!

• Mibi is now correctly named Mebi!
• The methods on Prefix no longer are part of a trait, and no longer take a reference to the prefix.
• The library no longer exports its enum members, only NumberPrefix and Prefix. It became confusing and bad style.