Add scss-lint gem for sass linting

Gemfile

@@ -108,7 +108,9 @@ end
 
 group :development do
   # Access an IRB console on exception pages or by using <%= console %> in views
+  gem 'scss_lint', require: false
   gem 'web-console', '3.3.0'
+
 end
 
 eval_gemfile './Gemfile_custom'

Gemfile.lock

@@ -397,6 +397,9 @@ GEM
       nokogiri (>= 1.4.0)
       nori (~> 2.4)
       wasabi (~> 3.4)
+    scss_lint (0.53.0)
+      rake (>= 0.9, < 13)
+      sass (~> 3.4.20)
     simplecov (0.14.1)
       docile (~> 1.1.0)
       json (>= 1.8, < 3)
@@ -541,6 +544,7 @@ DEPENDENCIES
   rvm1-capistrano3
   sass-rails (~> 5.0, >= 5.0.4)
   savon
+  scss_lint
   sitemap_generator (~> 5.3.1)
   social-share-button (~> 0.10)
   spring