Migrate to mysql

Now mysql is officially supported by gitlabhq. Follow next steps to migrate to mysql from sqlite

1. Get latest code
2. Install mysql
3. Save data - bundle exec rake db:data:dump RAILS_ENV=production
4. Change config to mysql using database.yml.example
5. Setup db - bundle exec rake db:setup RAILS_ENV=production
6. Restore old data - bundle exec rake db:data:load RAILS_ENV=production