Add test for Facebook app query string util function
Add test for FACEBOOK_TAB_URL setting
Add tests for signed request utility function

Tests for handling of empty signed request, changing the locale from Facebook format (underscore) to Playdoh format (hyphen) and a normal unwrap of a signed request object. Two utility functions are also added for use by the tests, one that creates a dummy dictionary to encode and the other to encode it.
Fix FACEBOOK_TAB_URL for Python 2.6
Add tests for get_best_locale util function
Pass get_best_locale tests

Convert locales to lowercase before comparing them. Use correct exception type for iterator that doesn't find a next item.
Refactor Download Tab tests into seperate files
Test facebookapps' js_redirect util function
Test facebookapps' facebook_locale decorator
Pass facebookapps' facebook_local tests
Test facebookapps' extract_app_data decorator
Refactor redirect assertion to TestCase subclass

Creates new TestCase subclassing `mozorg.tests.TestCase`.
Refactor JS redirect assertion to TestCase subclass

The facebookapps.utils.js_redirect test is now only a single method that calls this new assertion.
Center Download Tab features list
Test facebookapps' tab_redirect view
Pass facebookapps' tab_redirect view tests
Test Download Tab view

Tests for iframe allow, download button content and Facebook integration JavaScript hooks.
Implement Download Tab copy changes

Also adjust styles for copy changes.