separated the source into it's own model to allow multiple sources in one river
remove url from the river model
update seed data to include two sources
fix the controller test
remove APICache
add preliminary test for River#news method
add fixtures for the API data
mock the open method to use our fixture data
combine multiple sources in the River#news method
format the fixture xmls for readability
correct the fixture data
sort the combined list of news items by date