Add json response helper for tests

Aids in checking JSON responses from the server (found via
http://dhartweg.roon.io/rspec-testing-for-a-json-api)
Reorganize sessions controller tests
Add url validation for feed
Build out feed controller
Pull down feed data with feedjirra
Reorganize and add Feedbag
Add FeedParser class

Responsible for feed handling
Use first_or_create on feed#create
Organize feed model

Queue Sidekiq job after feed is created
Add sidekiq worker
Mount sidekiq Sinatra app
Add index for permalinks on articles
Add in rspec-sidekiq

Blocks jobs from being sent to Sidekiq queue when in test environment
Fix tests to work with feeds properly