change to using sassc

This is next in line for replacing sass-rails, and is a drop in replacement.

note that sass is still installed due to govuk-lint, however rails will now use sassc

Author: Anthony King

Gemfile

@@ -16,7 +16,7 @@ gem 'mysql2', '~> 0.5.2'
 gem 'notifications-ruby-client', '~> 3.1.0'
 gem 'puma', '~> 3.12'
 gem 'rails', '~> 5.2.2'
-gem 'sass-rails', '~> 5.0'
+gem 'sassc-rails'
 gem 'sentry-raven'
 gem 'uk_postcode', '~> 2.1', '>= 2.1.3'
 gem 'zendesk_api'

Gemfile.lock

@@ -277,12 +277,15 @@ GEM
     sass-listen (4.0.0)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
-    sass-rails (5.0.7)
-      railties (>= 4.0.0, < 6)
-      sass (~> 3.1)
-      sprockets (>= 2.8, < 4.0)
-      sprockets-rails (>= 2.0, < 4.0)
-      tilt (>= 1.1, < 3)
+    sassc (2.0.1)
+      ffi (~> 1.9)
+      rake
+    sassc-rails (2.1.0)
+      railties (>= 4.0.0)
+      sassc (>= 2.0)
+      sprockets (> 3.0)
+      sprockets-rails
+      tilt
     scss_lint (0.57.1)
       rake (>= 0.9, < 13)
       sass (~> 3.5, >= 3.5.5)
@@ -306,7 +309,7 @@ GEM
       sprockets (>= 3.0.0)
     thor (0.20.3)
     thread_safe (0.3.6)
-    tilt (2.0.8)
+    tilt (2.0.9)
     timecop (0.9.1)
     tzinfo (1.2.5)
       thread_safe (~> 0.1)
@@ -357,7 +360,7 @@ DEPENDENCIES
   rack-mini-profiler
   rails (~> 5.2.2)
   rspec-rails (~> 3)
-  sass-rails (~> 5.0)
+  sassc-rails
   sentry-raven
   shoulda-matchers (~> 4.0)
   simplecov