Avoid storyboard and UIWebView :balloon:

* Gemfile and Podfile update
* Removed storyboard, autolayout is done in code
* pass NSFetchedResultsController to detail view (we might
  use this to browse between multiple entries)
* removed uiwebview. content is displayed with
  NSAttributedText of UITextView

There is one bug left: starting EntriesViewController without
scrolling seems to disrupt the autolayout of the tablecells.
When scrolling down and up again, everything seems to be fine.