Update installation.md

Add the -y option to the python apt-get install commands to be consistent with the rest of the Document.
Merge pull request #5278 from ZaaLabs/master

Small consistency addition for installation.md
avatar upload on profile page
Use proper titles for issues trackers
Merge pull request #5281 from Popl7/upload_avatar_to_gitlab

avatar upload on profile page
Improve Profile settings UI
Merge pull request #5291 from astratto/title_issue_trackers

Use proper titles for issues trackers
Remove test case that cause Mysql Deadlock
API: new feature - remove project[D
API: specs for remove project
API: docs for remove project
Send devise emails async
Merge branch 'feature/api_remove_project' of /home/git/repositories/gitlab/gitlabhq
Reverted accidently removed registration module
Merge branch 'feature/devise_email_async' of /home/git/repositories/gitlab/gitlabhq