minor changes to parsing process, and map file content to structure.

- Move magic marker for unparsed sections to a constant to matcha
  against.
- Add functions to flatten a heckelement tree into a python structure

TODO

@@ -0,0 +1,7 @@
+Python:
+ - More options for accessing a heck tree.
+ - automated testing
+
+Guile, C (or D), and Haxe:
+ - Initial implementation
+