Use single snapshot version

[mdedetrich]

This trick is generally used in sbt plugins which use sbt-dynver that have scripted tests. Its means that whenever scripted tests run publishLocal it doesn't generate a new version and hence a new local publish every time which over time can pollute your local ivy repository.

In other words the version is just now

<@sbt-pull-request-validator>-<⎇ use-single-snapshot-version>-> sbt version
[info] welcome to sbt 1.9.7 (Amazon.com Inc. Java 1.8.0_402)
[info] loading global plugins from /Users/mdedetrich/.sbt/1.0/plugins
[info] loading settings for project sbt-pull-request-validator-build from plugins.sbt ...
[info] loading project definition from /Users/mdedetrich/github/sbt-pull-request-validator/project
[info] loading settings for project sbt-pull-request-validator from build.sbt ...
[info] set current project to sbt-pull-request-validator (in build file:/Users/mdedetrich/github/sbt-pull-request-validator/)
[info] 1.0.0-SNAPSHOT