Add the scss_lint gem

Gemfile

@@ -124,6 +124,7 @@ group :development do
   gem 'rack-handlers'
   gem 'xray-rails'
   gem 'haml-lint'
+  gem 'scss_lint', require: false
 end
 
 group :development, :test do

Gemfile.lock

@@ -550,6 +550,9 @@ GEM
     scenic (1.3.0)
       activerecord (>= 4.0.0)
       railties (>= 4.0.0)
+    scss_lint (0.53.0)
+      rake (>= 0.9, < 13)
+      sass (~> 3.4.20)
     sdoc (0.4.2)
       json (~> 1.7, >= 1.7.7)
       rdoc (~> 4.0)
@@ -715,6 +718,7 @@ DEPENDENCIES
   rspec-rails (~> 3.0)
   sass-rails (~> 5.0)
   scenic
+  scss_lint
   sdoc (~> 0.4.0)
   select2-rails
   sentry-raven