Upgrade scss-lint gem to v0.59.0

This loosens the Rake dependency so we can use Rake v13 and fixes a few
minor bugs:
https://github.com/sds/scss-lint/blob/master/CHANGELOG.md

Gemfile

@@ -372,7 +372,7 @@ group :development, :test do
 
   gem 'gitlab-styles', '~> 5.0.0', require: false
 
-  gem 'scss_lint', '~> 0.56.0', require: false
+  gem 'scss_lint', '~> 0.59.0', require: false
   gem 'haml_lint', '~> 0.36.0', require: false
   gem 'bundler-audit', '~> 0.6.1', require: false
 

Gemfile.lock

@@ -1081,9 +1081,8 @@ GEM
     sawyer (0.8.2)
       addressable (>= 2.3.5)
       faraday (> 0.8, < 2.0)
-    scss_lint (0.56.0)
-      rake (>= 0.9, < 13)
-      sass (~> 3.5.3)
+    scss_lint (0.59.0)
+      sass (~> 3.5, >= 3.5.5)
     securecompare (1.0.0)
     seed-fu (2.3.7)
       activerecord (>= 3.1)
@@ -1484,7 +1483,7 @@ DEPENDENCIES
   rugged (~> 0.28)
   sanitize (~> 5.2.1)
   sassc-rails (~> 2.1.0)
-  scss_lint (~> 0.56.0)
+  scss_lint (~> 0.59.0)
   seed-fu (~> 2.3.7)
   selenium-webdriver (~> 3.142)
   sentry-raven (~> 3.0)