Do not include Compilers-specific code in Compiler

By the way, I want to use ActiveSupport::Concerns to make the included
class_eval code cleaner.

lib/hamlit/compiler.rb

@@ -4,12 +4,7 @@ require 'hamlit/compilers/filter'
 require 'hamlit/compilers/preserve'
 require 'hamlit/compilers/script'
 require 'hamlit/compilers/text'
-require 'hamlit/concerns/escapable'
-require 'hamlit/concerns/registerable'
 require 'hamlit/filter'
-require 'hamlit/filters/css'
-require 'hamlit/filters/javascript'
-require 'hamlit/filters/ruby'
 
 module Hamlit
   class Compiler < Hamlit::Filter
@@ -19,11 +14,5 @@ module Hamlit
     include Compilers::Preserve
     include Compilers::Script
     include Compilers::Text
-    include Concerns::Escapable
-    extend  Concerns::Registerable
-
-    register :javascript, Filters::Javascript
-    register :css,        Filters::Css
-    register :ruby,       Filters::Ruby
   end
 end

lib/hamlit/compilers/filter.rb

@@ -9,6 +9,16 @@ module Hamlit
       BASE_DEPTH      = 2
       IGNORED_FILTERS = %w[ruby].freeze
 
+      def self.included(base)
+        base.class_eval do
+          extend Concerns::Registerable
+
+          register :javascript, Filters::Javascript
+          register :css,        Filters::Css
+          register :ruby,       Filters::Ruby
+        end
+      end
+
       def on_haml_filter(name, exp)
         exp = format_expressions(name, exp)
 

lib/hamlit/compilers/script.rb

@@ -3,6 +3,10 @@ require 'hamlit/concerns/escapable'
 module Hamlit
   module Compilers
     module Script
+      def self.included(base)
+        base.send(:include, Concerns::Escapable)
+      end
+
       def on_haml_script(*exps)
         exps     = exps.dup
         variable = result_identifier