Add 7.14-to-8.0 update guide

[ci skip]

doc/update/7.14-to-8.0.md

+# Update from 7.14 to 8.0
+
+## Notice
+
+__As of version 8.0, GitLab CI has been merged into GitLab CE and EE. Version
+8.0 of GitLab exists to ease the migration process and is required for
+converting an existing CI installation into an existing CE (or EE)
+installation.__
+
+For more information on the migration process, see the [migration docs].
+
+### 1. Stop CI server
+
+    sudo service gitlab_ci stop
+
+### 2. Switch to your gitlab_ci user
+
+```bash
+sudo su gitlab_ci
+cd /home/gitlab_ci/gitlab-ci
+```
+
+### 3. Get latest code
+
+```bash
+git fetch
+git checkout 8-0-stable
+```
+
+### 4. Install libs, migrations etc
+
+```bash
+# Install nodejs dependency:
+sudo apt-get install nodejs
+
+# For MySQL users
+bundle install --without postgres development test --deployment
+
+# For Postgres users
+bundle install --without mysql development test --deployment
+
+# Run migrations
+bundle exec rake db:migrate RAILS_ENV=production
+```
+
+### 5. Start web application
+
+    sudo service gitlab_ci start
+
+[migration docs]: http://doc.gitlab.com/ce/migrate_ci_to_ce/