duplicate tags in pom files

[hazel-sudz]

If you parse through https://oss.sonatype.org/content/repositories/snapshots/com/twitter/scalding-hadoop-test_2.11/0.18.0-RC3-1-a0516e0f-SNAPSHOT/scalding-hadoop-test_2.11-0.18.0-RC3-1-a0516e0f-SNAPSHOT.pom

you can see that scm is duplicated twice. This causes some issues with automated ingestion tools such as artifactory maven proxy.

the ingestion crash is: Duplicated tag: 'scm' (position: START_TAG seen ...</licenses>\\n <scm>... @27:10) ."

[hazel-sudz]

https://github.com/sbt/sbt-ci-release suggests that this info is automatically populated and does not need to be manually added:

By installing sbt-ci-release the following sbt plugins are also brought in:

[sbt-dynver](https://github.com/dwijnand/sbt-dynver): sets the version number based on your git history
[sbt-pgp](https://github.com/sbt/sbt-pgp): to cryptographically sign the artifacts before publishing
[sbt-sonatype](https://github.com/xerial/sbt-sonatype): to publish artifacts to Sonatype
[sbt-git](https://github.com/sbt/sbt-git): to automatically populate scmInfo