Store flash messages in a different session variable

Avoids conflict with how Rails 3/public_website deals with flash messages
Merge branch 'flash-session-key'
Add rubocop to .gitignore
Merge pull request #530 from moneyadviceservice/rubocop

Add rubocop to .gitignore
Add page limit to news index
Remove block from news reader

News reader is always returning	a collection
Merge branch 'ten-results-per-page'
Use news description instead of intro
Merge pull request #532 from moneyadviceservice/news-descriptions

Use news description instead of intro
Add Feedback entity.
Setup ActionMailer.
Add a basic feedback repository with a private mailer.
Add a FeedbackWriter interactor.
Add dough.
Refactor feedback entities to cover different types of feedback.
Implement feedback page for articles.
Implement general (technical) feedback page.
Implement the money advice page.
Add links to give feedback to the article show page.
Put the feedback panel on articles behind a feature toggle.