Prefer sbt-ci-release

[ignasi35]

Refs akka/akka-http#3792 and #3221

Publishing snapshots to Sonatype requires the version to be suffixed -SNAPSHOT but sbt-dynver doesn't use that on its version name scheme. I think ( I checked) sbt-ci-release handles that out of the box.

Pitfalls:

• by default sbt-ci-release does a direct stage/close/promote on sonatype instead of the just stage (with close/promote manually after) but probably that's just a default
• ( sbt-ci-release does it ) the final implementation should still do a bundle upload
• vegemite's release script runs sbt release whilc sbt-ci-release uses its own sbt ci-release so this issue is probably blocked by (or related to) Support release by tag #3239