Move the parse method out of Tag, only blocks need the body parsed.

The parse method should be renamed to something like parse_body,
since that is how it is used, and no non-block tags were using the
parse method.

lib/liquid/block.rb

@@ -5,6 +5,11 @@ module Liquid
     FullToken         = /\A#{TagStart}\s*(\w+)\s*(.*)?#{TagEnd}\z/om
     ContentOfVariable = /\A#{VariableStart}(.*)#{VariableEnd}\z/om
 
+    def initialize(tag_name, markup, tokens)
+      super
+      parse(tokens)
+    end
+
     def blank?
       @blank || false
     end

lib/liquid/tag.rb

@@ -19,9 +19,6 @@ module Liquid
       @options    = options
     end
 
-    def parse(tokens)
-    end
-
     def name
       self.class.name.downcase
     end

lib/liquid/tags/include.rb

@@ -35,9 +35,6 @@ module Liquid
       end
     end
 
-    def parse(tokens)
-    end
-
     def blank?
       false
     end