Fetching and Parsing Feeds

* Set dashboards#show as root_path for signed_in users
* Add Feedjira to Gemfile
* Add sources and feed_entries tables to database
* Add fetching and parsing methods to source and feed_entry models
* Show user.timeline on dashboards#show
* User can see sources#index
* User can add new sources
I'm concerned about all these class methods, perhaps a different object would be good here some kind of factory?