Release 5.0.0 - Juno

This patch updated the README to reflect the current version and
include release notes.

Changes in this release:
* Pinned vcsrepo dependency to 2.x
* Bumped stdlib dependency to 4.x
* Added ability to hide secrets from puppet logs
* Removed orphaned os_concat function
* Removed dependencies on mysql and postgresql devel libraries

Change-Id: I4d3a497304219d4a19789f447c83f4b90f2a5846