Update UI for Loop and Relationship fields to utilize dashicons if the environment is WordPress 3.8-alpha or higher. Maintains backwards compatibility by checking the WordPress version and appending a body class of mp6 if applicable. All CSS utilizes this body class if available, else the UI remains as-is.
Merge pull request #184 from jchristopher/ui-updates

Updates UI for Loop and Relationship fields in WordPress 3.8+