Use 'latest.integration' for version in README

[wsargent]

From https://underscore.io/blog/posts/2015/11/09/sbt-commands.html#latest-dependencies

Ivy dependencies allow you to select “latest.integration” as the revision number:

addSbtPlugin("org.ensime" % "ensime-sbt" % "latest.integration")

This will give you the latest and greatest version. Use it for global plugins (see below) for you development environment. Avoid it for core build dependencies because you want a reproducible build at all times.