Don't enforce rbenv version

Fix broken commit link in branches page

It would be better not include either rbenv or a specific rbenv version
with gitlab.

Incorrect line numbering in diff

When displaying a diff, the line number always starts at one, even if the first diff is not at the first line
Fixes this to display correct line numbering on first diff

Conflicts:
	app/views/layouts/_project_menu.html.haml

This makes gitlabhq compatible with more LDAP servers (specifically OpenLDAP).