Get process to easily publish a JAR set up

[JGulbronson]

We should have a script to easily create a JAR (and optionally publish it), so we can release easily and often. @swankjesse I think you mentioned you'd be okay to take this on?

[maniksurtani]

./gradlew clean jar?

[maniksurtani]

(That doesn't publish it anywhere though)

[swankjesse]

We have a guide:
https://github.com/square/misk/blob/master/RELEASING.md

I’d prefer something even easier for releases that don’t go all the way to Maven Central.