Make the engine Rails 5+ compatible

This PR makes the engine compatible with rails 5+ versions.

Author: dixpac

Gemfile.lock

@@ -2,7 +2,7 @@ PATH
   remote: .
   specs:
     tailwindcss-rails (0.4.1)
-      rails (>= 6.0.0)
+      rails (>= 5.0.0)
 
 GEM
   remote: https://rubygems.org/
@@ -71,23 +71,21 @@ GEM
     concurrent-ruby (1.1.9)
     crass (1.0.6)
     erubi (1.10.0)
-    globalid (0.5.2)
-      activesupport (>= 5.0)
+    globalid (0.4.2)
+      activesupport (>= 4.2.0)
     i18n (1.8.10)
       concurrent-ruby (~> 1.0)
-    loofah (2.12.0)
+    loofah (2.10.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     mail (2.7.1)
       mini_mime (>= 0.1.1)
     marcel (1.0.1)
     method_source (1.0.0)
     mini_mime (1.1.0)
-    mini_portile2 (2.6.1)
     minitest (5.14.4)
-    nio4r (2.5.8)
-    nokogiri (1.12.3)
-      mini_portile2 (~> 2.6.1)
+    nio4r (2.5.7)
+    nokogiri (1.11.7-x86_64-darwin)
       racc (~> 1.4)
     racc (1.5.2)
     rack (2.2.3)
@@ -119,7 +117,7 @@ GEM
       method_source
       rake (>= 0.13)
       thor (~> 1.0)
-    rake (13.0.6)
+    rake (13.0.3)
     sprockets (4.0.2)
       concurrent-ruby (~> 1.0)
       rack (> 1, < 3)

tailwindcss-rails.gemspec

@@ -13,5 +13,5 @@ Gem::Specification.new do |spec|
 
   spec.files = Dir["{app,lib}/**/*", "MIT-LICENSE", "Rakefile", "README.md"]
 
-  spec.add_dependency "rails", ">= 6.0.0"
+  spec.add_dependency "rails", ">= 5.0.0"
 end