Fix lists not become 100% width when on mobile

There was an issue on production where the list module were not changing
to fill the complete width of page when the width was reduced.

It turns out that we had column code knocking around in a few places in
our scss codebase. I have collapsed them down to one set of styling
columns shared between the homepage and modules.
Replace cucumber in grunt tests with cheapseats
Remove Cucumber and feature tests

- Stop not linting the features directory
- Remove Cucumber from the Gruntfile and package.json
- Update the README to reflect cheapseats
- Remove config related to Cucumber tests
- Remove feature tests

Our feature tests have moved from Cucumber to JavaScript, so the
tests themselves are no longer in this app.
Purge Ruby

- Stop installing gems on Travis
- Remove Gemfile
- Update README, Jenkins script and start-app.sh to remove bundle install
  step
Merge pull request #345 from alphagov/feature/cheapseats-integration

Replace cucumber in grunt tests with cheapseats
Merge pull request #344 from alphagov/fix-column-styling

Fix lists not become 100% width when on mobile
Prevent tables from throwing an error if empty
Merge pull request #347 from alphagov/bugfix/table-crash-with-no-data

Prevent tables from throwing an error if empty