Added basic app feed classes to hold the information from an app feed.
Added basic feed reader and xml example. The xml example is very much based off
of the "Sparkle" updater.
Fixed imports in AppFeedReader and corrected constructor errors.
Fixed app feed test/example file.
Completed RSS parsing. Added tests for parser.
Added .travis.yml for builds and testing through Travis-CI.
Merge branch 'feature/appfeeds'

AppFeeds are now readable and this feature is finished. This branch has been tested
and should now be merged into the development branch 'master'.