Push deployed artifact to sonatype on tagged release

[Vic Kumar]

Should automate pushing to the sonatype repo - should be tied into the git tag.

i.e., if the current version of the software is 99.99.0, then:

git commit -a -m "v99.99.1"
git tag -a 99.99.1 -m "v99.99.1"
git push origin master
git push --tags origin

would trigger a new deploy artifact.

Artifacts are deployed using the sbt-sonatype plugin.