WIP on the layout of the feeds view.

Currently trying to implement a mock of an accordion menu.
More work on the side menu.
Removed a <br> from the HTML generated if there are notices/errors in the flash.

The <br> was never removed after closing the notice/error, which is not the expected behavior.
Fix importing of SCSS partial style files.

Change arrow icon when opening a folder (closed -> arrow-right, opened -> arrow-down).
Use alternative white icons for folders. Add RSS icon to feed menu.
Add javascript to highlight (add class "active") only the last feed user clicked on.
Feed index view shows only feeds the user is suscribed to.
Moved sidebar menu to its own view fragment. Added method to Feed model to retrieve items from a feed.
Fixed broken tests.
Nicer feed view.

For the moment a single feed is visualized. Still a lot of work to do, but the feeds view is starting to look more final.
Fixed navbar to the top of the page. Made sidebar a bit narrower.
Fixed broken tests.

There were two problems:

- FactoryGirl was generating URLs with underscores for the feeds. Open-uri throws an error when asked to open such an URL.

- The acceptance test for the feeds view failed because it was trying to open an URL generated by FactoryGirl which, of course, doesn't actually exist (nor does it have a RSS document). For the moment I've changed the test so that real RSS URLs are used; this means that these URLs are actually retrieved during acceptance testing, which is not something I'm happy with. I will change it as soon as possible: tests should never depend on external services or APIs.

The possible long-term solution for the second problem could be to use the RestClient class instead of Open-uri, and substitute it with a mock during acceptance testing.

Or better yet, maybe we should retrieve RSS feeds with a background job instead of during a user process; this way acceptance testing would never trigger an HTTO download. A side benefit would be better performance for the user processes, at the cost of increased complexity in the code.
Sanitize feed item fields in the model, not in the view.