Revert "Update POM version numbers to 5.0.0-rc2"

This reverts commit ceb3c487984ba48b210af85cfd97c65ed0f7a540.
Update last version number to 5.0.0-rc2
Fix logback.xml XML header

`mvn` without this commit complained about
the logback.xml file (loudly).
Merge pull request #912 from joshmoore/fix-logback

Fix logback.xml XML header
Merge pull request #905 from melissalinkert/rc2-revert

Revert "Update POM version numbers to 5.0.0-rc2"