HR-226 - hrabsence - Add skeletal extension
HR-226 - civicrm/absences - Add skeletal page
HR-226 - civicrm/absences - Replace boilerplate with empty Marionette page
HR-226 - civicrm/absences - Add CSS file
HR-226 - civicrm/absences:

 * Add placeholder markup
 * Add models/collections for filtering mechanism
HR-226 - civicrm/absence - First option in dropdowns should be placeholder
HR-226 - civicrm/absences - Add tab placeholders
HR-226 - civicrm/absences - Demonstrate refresh/live-update based on filter options
HR-226 - civicrm/absences - Highlight the current selection
Merge pull request #273 from civicrm/master-absence

HR-226 - Implement skeletal "Absences" page with Marionette