Working with a custom fragment pager adapter.
Now using ViewPager and custom pager adapter.
MainActivity now holds a view pager and pager adapter. Tabs are now implemented (with some TODOs, however).
Refactoring the fragments to have them implement the newInstance() "pattern". View pager now fuly working.
MainActivity implements OnPageChangeListener to enable us to update the action bar currently selecte navigation tab when a scroll occurs in the view pager. Get fact icon is now the download icon.