Make API less surprising by unifying new and with_key? #146

In light of a possible 2.0 version of this crate, would it be possible to unify the constructors new and with_key of SlotMap into a single new constructor?

In my understanding, the convention for with_ constructors is that they take additional parameters (e.g. Vec::with_capacity). But here with_key implies something about the type of the collection. In addition, it is confusing that SlotMap with a key type different from the default does not offer a new default constructor.

One way to resolve both issues would be to make DefaultKey the default for the first generic argument of the SlotMap type. Wouldn’t this result in a less surprising API?