Move generation logic to new Generator class

assets/parser.d.erb

@@ -1,8 +1,8 @@
-<% if @modulename %>
-module <%= @modulename %>;
+<% if @grammar.modulename %>
+module <%= @grammar.modulename %>;
 
 <% end %>
-class <%= classname %>
+class <%= @classname %>
 {
     enum
     {
@@ -117,7 +117,7 @@ class <%= classname %>
             uint accepts;
         }
 
-<% transition_table, state_table = lexer.build_tables %>
+<% transition_table, state_table = @lexer.build_tables %>
         private static const Transition transitions[] = [
 <% transition_table.each do |transition_table_entry| %>
             Transition(<%= transition_table_entry[:first] %>u, <%= transition_table_entry[:last] %>u, <%= transition_table_entry[:destination] %>u),