Replace 6.0-to-6.4.md with 6.0-to-6.5.md
 Merge branch 'doc/6-0-to-6-5' into 'master'

Replace 6.0-to-6.4.md with 6.0-to-6.5.md
Remove GitHub mention because we also have a GitLab issue tracker now.
 Merge branch 'remove-github' into 'master'

Remove github specific mention of issue tracker
Warn against RVM.
Spelling mistake and add links.
No need for code tag here.
 Merge branch 'ugly-reference' into 'master'

Ugly Reference

This prevents it displaying as < code > on https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/install/installation.md
 Merge branch 'warn-against-version-managers' into 'master'

Warn Against Version Managers
Merge branch 'master' of github.com:gitlabhq/gitlabhq