Update to latest version of oss-parent POM

Signed-off-by: Stuart Halloway <stu@thinkrelevance.com>
Add Sonatype OSS release profile

Using nexus-staging-maven-plugin. Adapted from the procedure developed
for contrib libraries at https://github.com/clojure/build.poms

Signed-off-by: Stuart Halloway <stu@thinkrelevance.com>
Merge branch '1.5.x'