Set core.rrb-vector to test only on Clojure 1.5.1+

core.rrb-vector will work on any version after 1.5.0, but since 1.5.0
was a buggy release we do not currently have tests configured for
1.5.0, just 1.5.1.
Set extra Sonatype release goals in release job template

This automates the last step of a release, which is "releasing" the
staging repository created by the Sonatype Nexus Staging Maven plugin.

We have struggled with this in the past, see
https://issues.sonatype.org/browse/OSSRH-5976
and
https://github.com/sonatype/nexus-maven-plugins/issues/37

But it appears to be working now:
http://build.clojure.org/job/core.rrb-vector/7/