add steps to monthly releases
Update installation guide with new shell version.
remove redudant text in release doc
Merge branch 'detailed-monthly-release' into 'master'

Detailed monthly release

Fixes #1190
Merge branch 'shell_version_install_doc' into 'master'

Update Shell version in the Install doc
Merge branch 'master' of https://github.com/gitlabhq/gitlabhq