Create asset sync initialiser to set Rackspace configuration
user
```ruby
AssetSync.configure do |config|
  config.fog_provider = ENV['FOG_PROVIDER']
  config.rackspace_username = ENV['RACKSPACE_USERNAME']
  config.rackspace_api_key = ENV['RACKSPACE_API_KEY']

  # if you need to change rackspace_auth_url (e.g. if you need to use Rackspace London)
  config.rackspace_auth_url = ENV['RACKSPACE_AUTH_URL']
  config.fog_directory = ENV['FOG_DIRECTORY']

  # Invalidate a file on a cdn after uploading files
  # config.cdn_distribution_id = "12345"
  # config.invalidate = ['file1.js']

  # Increase upload performance by configuring your region
  config.fog_region = 'lon'
  #
  # Don't delete files from the store
  config.existing_remote_files = 'delete'
  #
  # Automatically replace files with their equivalent gzip compressed version
  config.gzip_compression = true
  #
  # Use the Rails generated 'manifest.yml' file to produce the list of files to
  # upload instead of searching the assets directory.
  # config.manifest = true
  #
  # Fail silently.  Useful for environments such as Heroku
  # config.fail_silently = true
end
```
assistant