Upgrade frontend toolkit to version 5.0.1

- Removed phase-banner scss file as no longer needed

Full list of changes:

SelectionButtons will add a class to the label with the type of the child input
alphagov/govuk_frontend_toolkit#317

Add GOVUK.ShowHideContent JavaScript to support showing and hiding content, toggled by radio buttons and checkboxes
alphagov/govuk_frontend_toolkit#315

Fix error in IE - remove trailing comma from shimLinksWithButtonRole JavaScript
alphagov/govuk_frontend_toolkit#323

Remove unnecessary print font fallback that causes regression downstream
alphagov/govuk_frontend_toolkit#328

Update tooling to use npm script rather than grunt-shell
alphagov/govuk_frontend_toolkit#327

For smaller screens (<768px) ensure that the GOVUK.StickAtTopWhenScrolling JS "unsticks" the element which was previously "stuck" (by removing both the class which sets fixed positioning and the shim).
alphagov/govuk_frontend_toolkit#329

Lint codebase using standard
alphagov/govuk_frontend_toolkit#334

Add semicolons at the start of IIFE's
alphagov/govuk_frontend_toolkit#339

Removal of external link styles and icons, if you are using the external-link-* mixins you will need to remove them from your codebase
alphagov/govuk_frontend_toolkit#293

Correct spelling of the 'accordion' icon, you will need to check for the incorrect spelling 'accordian' and update if you are using this icon
alphagov/govuk_frontend_toolkit#345

Amend GOVUK.StickAtTopWhenScrolling to resize the sticky element and shim when the .js-sticky-resize class is set
alphagov/govuk_frontend_toolkit#343

Allow custom options in GOVUK.analytics.trackPageview
alphagov/govuk_frontend_toolkit#332

Fix role="button" click shim
alphagov/govuk_frontend_toolkit#347

Make font variables lowercase
alphagov/govuk_frontend_toolkit#348

Update selection button documentation
alphagov/govuk_frontend_toolkit#350

Change colour used in phase tags to govuk-blue
alphagov/govuk_frontend_toolkit#353

Gemfile.lock

@@ -120,7 +120,7 @@ GEM
       govuk_frontend_toolkit (>= 4.14.1)
       rails (>= 4.1.0)
       sass (>= 3.2.0)
-    govuk_frontend_toolkit (4.16.1)
+    govuk_frontend_toolkit (5.0.2)
       rails (>= 3.1.0)
       sass (>= 3.2.0)
     govuk_template (0.19.1)
@@ -155,7 +155,7 @@ GEM
     method_source (0.8.2)
     mime-types (2.99.3)
     mini_portile2 (2.1.0)
-    minitest (5.10.0)
+    minitest (5.10.1)
     multi_json (1.11.2)
     multi_test (0.1.2)
     multipart-post (2.0.0)