Added RefreshJob model.

Instances of this model will represent ocurrences of a user requesting a feed refresh, and through them the app will be able to inform the user of the status of such requests.
Renamed RefreshJob model to RefreshFeedJob. Added unit tests for the association between feeds, users and refresh_feed_jobs.
Added unit tests for the RefreshFeedJob model.
Removed unit tests file that had been added by mistake.
Added test stubs for running feed updates in background when a user manually requests them.
Moved the code that updates a feed to a new class lib/feed_updater. UpdateFeedJob just invokes this class.

This enables us to create a different job for when the update is manually requested by a user. This job will receive as an additional argument the id of the user, will also invoke lib/feed_updater and additionally will update the status of the job in the database, so that the user can see this status in the view.
Renamed RefreshFeedJob model to RefreshFeedJobStatus.

The convention is that classes with names ending in "Job" are Resque job classes. It's a bad idea having an ActiveRecord model named like that. Hopefully the new name is less confusing. I know it's a verbose class name. I've been programming enterprise java for years before coming to rails, I may have issues. Leave me alone or send me a pull request with better naming.
Renamed UpdateFeedJob to ScheduledUpdateFeedJob.

This is in anticipation of the new job that will be created to update a feed when a user manually requests it.
WIP: background job to process user-requested feed refreshes.
Removed unnecessary require lines from jobs.
Finished implementing background job for user-requested feed refreshes.

This job can mark a feed as "available" and "not currently failing" if the update is successful, same as the scheduled updates. However it does not change the schedule itself; perhaps in the future this could be desirable, but right now it's too complex and would need further thought.
The User.refresh_feed method now doesn't fetch the feed, but rather it enqueues a job to fetch it (and creates a database record to indicate that the refresh job is running).
Fixed FeedsController unit test.
Added controller and routes for the client to query about refresh jobs requested by the current user and their status.
Moved the angularjs code that displays the start page to a new angularjs service.

This way the method can be invoked from other methods (e.g. when the user requests a feed refresh).
When the angularjs app loads, by default load the start page.

This doesn't add anything right now, but in the future will start timers to update the status of any jobs that are running, the status of which will be displayed in the start page.
WIP: display status of refresh jobs in the start page, and display an alert when such a job finishes.

I've decided not to return full data for the related feeds when returning a JSON document with the refresh_feed_job_statuses. It's too verbose and in many cases redundant; it will be the responsibility of the client to request the information of any feed which is not already in the scope.
The JSON with the array of refresh_feed_job_statuses is obtained though the #index action, instead of #show.
Added error handling to DataImportsController#show
Added show action to RefreshFeedJobStatusesController, to retrieve JSON describing a single refresh_feed_job_status.