update guide from 7.9 -> 7.10

doc/update/7.9-to-7.10.md

+# Update from 7.9 to 7.10
+
+## Notice
+
+__GitLab CI 7.10 requires GitLab 7.10 or higher and GitLab CI Runner v5__
+
+### 1. stop CI server
+
+    sudo service gitlab_ci stop
+
+### 2. Switch to your gitlab_ci user
+
+```
+sudo su gitlab_ci
+cd /home/gitlab_ci/gitlab-ci
+```
+
+### 3. Get latest code
+
+```
+git fetch
+git checkout 7-10-stable
+```
+
+#### Redis config
+
+If you have `config/resque.yml` file - please update it with recent `config/resque.yml.example`
+
+### 4. Install libs, migrations etc
+
+
+```
+# 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