Update haml-lint for HAML 5

https://github.com/brigade/haml-lint/issues/247#issuecomment-308332241

Gemfile

@@ -232,7 +232,7 @@ gem 'dalli'
 group :development do
   # to launch specs when files are modified
   gem 'guard-rspec'
-  gem 'haml_lint', '~> 0.24.0'
+  gem 'haml_lint'
   gem 'spring-commands-rspec'
   # for static code analisys
   gem 'rubocop', require: false

Gemfile.lock

@@ -219,11 +219,11 @@ GEM
       haml (>= 4.0.6, < 6.0)
       html2haml (>= 1.0.1)
       railties (>= 4.0.1)
-    haml_lint (0.24.0)
+    haml_lint (0.28.0)
       haml (>= 4.0, < 5.1)
       rainbow
       rake (>= 10, < 13)
-      rubocop (>= 0.47.0)
+      rubocop (>= 0.50.0)
       sysexits (~> 1.1)
     hashdiff (0.3.7)
     hashie (3.5.7)
@@ -644,7 +644,7 @@ DEPENDENCIES
   gravtastic
   guard-rspec
   haml-rails
-  haml_lint (~> 0.24.0)
+  haml_lint
   iso-639
   jquery-datatables-rails
   jquery-rails