[FEEDS] - Added Flickr and Youtube support

* Re-engineered base fetch method in feeds to now allow for discrete AJAX/JSONP results
* Added Youtube and Flickr templates
* Added tabbed example to examples page to demonstrate interoperability of widgets

** Known issues - Multimedia player seems to only register one Youtube instance even though ```wb.add``` is used for rebinding and init. 

/cc @laurentgoderre