Refactored discoverFeeds

Deprecated google-feeds.js, added reader.fetch.discoverFeeds function to
fetch.js, greatly simplified the function, changed options to use the
new function. Added new replaceBRs utility function.
Changed how fav icons are retrieved

Deprecated util.getFavIconURL, added reader.fetch.getFavIconURL, updated
dependencies
Minor comment changes
Comment cleanup
New libs
Added fetchFeed function

In prep of deprecating feed-http-request.js