Edit GitHub Flow url
Update the help/update docs to include omnibus as well.
Merge branch 'gitlab_flow_edit' into 'master'

Gitlab flow edit

Changed GitHub Flow links

See merge request !201
Merge branch 'missing_update_links' into 'master'

Missing omnibus update links in help/update

I took the liberty and refactored it a little. Open issue https://gitlab.com/gitlab-org/omnibus-gitlab/issues/269

Here is a screen

![gitlab_update_page](https://gitlab.com/uploads/axil/gitlab-ce/0395154f23/gitlab_update_page.png)

See merge request !202