Bump govuk_frontend_toolkit gem to 4.14.0

This commit bumps the front-end toolkit from 4.8.0 to 4.14.0 as a result
of the recent update to the front-end toolkit.

* alphagov/govuk_frontend_toolkit#296
* alphagov/govuk_frontend_toolkit#294
* alphagov/govuk_frontend_toolkit#292

SmartAnswers makes use of the following files from the frontend_toolkit:
Stylesheets:
- _conditionals.scss
- _typography.scss
- _colours.scss
- _shims.scss
- design-patterns/_buttons.scss
- _grid_layout.scss

Javascript:
- govuk/multivariate-test

Having reviewed the diff between 4.8.0 and 4.14.0 alphagov/govuk_frontend_toolkit@0cfc216...37d23c1.

This diff composes of 82 commits, 34 Merge Commits and 48 concrete commits.

I gone through each tracing the possible areas that this might affect smart answers. To the best of my knowledge I have found only cosmetic changes to the following files.

Stylesheets:
- _typography.scss e05ca517 , 70f53d27c
- _colors.scss 11798945a , 3853a726c , 0052024b4b9 , 984d53292 , 2180a72e4

UI examination was carried by Anika and myself and we found nothing of concern.

Already existing unit, regression and integration tests passed, giving assurance
that the aforementioned commit/changes have had no (interfering) affect to the
transit route or flow or other routes within check uk visa or other smart answers.

Gemfile

@@ -9,7 +9,7 @@ gem 'ast'
 gem 'gds-api-adapters', '~> 30.6'
 gem 'govspeak', '~> 3.3.0'
 gem 'govuk-content-schema-test-helpers', '~> 1.3.0'
-gem 'govuk_frontend_toolkit', '4.8.0'
+gem 'govuk_frontend_toolkit', '4.14.0'
 gem 'htmlentities', '~> 4'
 gem 'json'
 gem 'logstasher', '0.4.8'

Gemfile.lock

@@ -90,7 +90,7 @@ GEM
     govuk-lint (0.7.0)
       rubocop (~> 0.35.0)
       scss_lint (~> 0.44.0)
-    govuk_frontend_toolkit (4.8.0)
+    govuk_frontend_toolkit (4.14.0)
       rails (>= 3.1.0)
       sass (>= 3.2.0)
     htmlentities (4.3.3)
@@ -268,7 +268,7 @@ DEPENDENCIES
   govspeak (~> 3.3.0)
   govuk-content-schema-test-helpers (~> 1.3.0)
   govuk-lint
-  govuk_frontend_toolkit (= 4.8.0)
+  govuk_frontend_toolkit (= 4.14.0)
   htmlentities (~> 4)
   json
   logstasher (= 0.4.8)