refactor core data setup in app delegate

- managed object context, moc, is a static variable
- instance method managedObjectContext returns the moc

TODO - prove we don't need the property managedObjectContext that was
part of the example used in class, then remove
add AudioClip entity to Model
setup feed to fetch AudioClips
add controller - FinalizeRecording

- recording's output file's name is timestamped
- update navigation item colors to salmon
- update toolbar item colors to charcoal
navigation bar updates for FinalizeRecording controller

- replaces 'share' with iOS7 share / action icon
- overrides navigation controller's default back button with 'Edit' and
  action that pops the controller
refactor feed's datasource to load from fetcher's fetched objects
remove seed data from feed
organize file, add pragma marks to more clearly identify concerns
setup asynch API request to Heroku for data in the feed, log the returned JSON
Feed loads seed data from Heroku API

- adds a fetchFromCoreData method
- adds a loadDataFromHeroku method
- if data's already there we just load from Core Data
- attributes are hacky: api's name attr is really an audioClip's title,
  createdAt is assigned on the fly, etc
add audioURL attr to AudioClip
save audio data to AudioClip instances

- if API call is made an additional call is made to save audio data to
  its owner
- rips out hard-coded player assignment to testaudio.m4a
- player alloc/init'd for each new play, set to nil on finish
- removed some synthesized properties left over from previous seed data