Add maven gpg plugin to pom, to sign jar pending upload to mvn central
Add version attribute to gpg plugin stanza
Central repo requires a developer stanza I believe
Add sonatype POM as parent as we will be pushing Jars here.

This is the easiest way to get jars into central repository (without
hosting stuff ourselves).
Add developerConnection to the scm block
Add publishing documentation outlining steps to release a JAR
Move gpg signing plugin into a profile so we don't use it on Travis
Merge pull request #6 from smulube/publishing

Publishing config and information