Move server_version_num from trait to impl

[AtkinsChang]

No description provided.

[abonander]

Renaming a trait is a breaking change and so will have to wait until 0.6.0, which we'll be working on over the next few weeks.

[abonander]

Actually, looking at this now, I don't really see a reason why it should be a trait and not just an inherent method on PgConnection.

PoolConnection<Postgres> dereferences to PgConnection so calling .server_version_num() on it should work with just the impl for PgConnection.

[AtkinsChang]

you are right, I mark this trait deprecated

Ohh, it has been released 😢

[abonander]

Oh yeah sorry, my mistake. I didn't realize that we hadn't actually put out a release with this trait definition in it yet.

Don't worry about marking it deprecated, we're now going to start preparing the 0.6.0 release so you can just convert the trait to a simple inherent method on PgConnection.