added sources dict and conducted testing

output tabari formatted event file where key is reverse url of story.
e.g., story

'http://stream.wsj.com/story/latest-headlines/SS-2-63399/SS-2-444966/'s
key is:

/669444-2-SS/99336-2-SS/senildaeh-tsetal/yrots/moc.jsw.maerts//:ptth