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
If @feed_entries is an empty array you can do the following

```erb
<%= render(@feed_entries) or render("no_sources") %>
```

This might not actually be the best now that I'm thinking about it, but I don't like the controller setting up the partial name.