resolves #55 sort attribute entries in document header

lib/kramdown-asciidoc/writer.rb

@@ -125,7 +125,12 @@ def empty?
     end
 
     def to_s
-      (@header.empty? ? @body : (@header + (@body.empty? ? [] : [''] + @body))).join LF
+      if @header.empty?
+        @body.join LF
+      else
+        attrs, others = @header.partition {|it| it.start_with? ':' }
+        (others + attrs.sort + (@body.empty? ? [] : [''] + @body)).join LF
+      end
     end
   end
 end; end

spec/scenarios/attributes/sorting.adoc

@@ -0,0 +1,6 @@
+= Document Title
+:bar: bar
+:experimental:
+:foo: foo
+
+menu:Terminal[Quit]

spec/scenarios/attributes/sorting.md

@@ -0,0 +1,3 @@
+# Document Title
+
+**Terminal > Quit**

spec/scenarios/attributes/sorting.opts

@@ -0,0 +1,3 @@
+:attributes:
+  foo: 'foo'
+  bar: 'bar'

spec/scenarios/heading/lazy_ids/auto-ids.adoc

@@ -1,6 +1,6 @@
 = Document Title
-:idseparator: -
 :idprefix:
+:idseparator: -
 
 == A Section