Communicate applicationCache status

check-cache.coffee

appCache = window.applicationCache;
appCache.addEventListener "cached", (event) =>
  # show good message
appCache.addEventListener "noupdate", (event) =>
  # show good message
appCache.addEventListener "updateready", (event) =>
  # swap out cache and let user know new page available
  # reload page to get latest
  appCache.swapCache()
appCache.addEventListener "error", (event) =>
  # we will get an error if offline
  if app.OfflineSupport.workOffline
    # show good message
  else
    # show bad message, reload page to fix