Fixes #5144 Refs #4996

Added .ruby-version & .ruby-gemset in .gitignore

Drop support of root namespace in model

Don't show users password change page if ldap users

Fix issue_closing_regex in gitlab.yml.example

It turns out that regex escapes and YAML quoted-scalar escapes don't play
nicely together.

Update unicorn.rb.example

[WIP]Drop support of root namespace in routing

Add "public-project?" checkbox to new-project view 

Minor UI fix in views/public/project/index.html.haml

Fix typo in installation.md

Re-enable notifying commit authors of new commit notes