Postgres Driver is not found

<dependency>

            <groupId>org.postgresql</groupId>

            <artifactId>postgresql</artifactId>

            <version>42.1.4</version>

            <scope>compile</scope>

        </dependency>

Needs to be added to spigot server's pom.xml

Took a while to figure out the process here, but I have confirmed it fixes postgres support in my plugin.

Thanks in advance =) it can wait until I can submit a PR if you like.