Version check functionality

@JobV can you turn the text below into a blog post?

We're working on a version check function for GitLab to reduce the problem of outdated servers. These servers are a security problem, provide a bad user experience and lead to issues being created with problems that have already been solved. By making outdated installations visible to its users we hope that people will upgrade sooner.

The version check will work in the following way. The /help page of GitLab will load an image from version.gitlab.com. This image will show green for an up to date version, yellow for an out of date version and red for a missing security update.

The image requests parameters requests will contain the GitLab version and the server hostname. We'll store each request with a timestamp, the GitLab version and the server hostname. We will not store the user ip-address. We will send the server hostname to have more information about where and how GitLab is used. Loading external images is similar to how the gravatar images of users are used. Just like the gravatar images you will be able to to turn off the functionality if you don't want your GitLab server to connect outside the firewall. The version check functionality can be disabled in the application settings.

Providing the new package server and the version check server requires constant maintenance and operational capacity. Getting better insight into where and how GitLab is used will help us improve GitLab for everyone. We realize that it sending the server hostname by default is not a trivial action and not everyone will be happy about this. We think that ensuring the sustainability of GitLab package server and version check services makes it a good trade-off. There will always be an option to turn this behaviour off. Please let us know what you think about the above plan in the comments.