Get XML validation back into a sane state.  (This is a follow-up to r86.)
Get XML validation back into a sane state.  (This is a follow-up to r86.)

* lib/tk_data.py
  (TKDataParser._validate_tag): Rework this logic for, uh, accuracy.
  (TKDataParser.startElement): Enable tag stack validation.
  (TKDataParser.endElement): Remove validation logic -- xml.sax does
    this bit for us.

cmpilato/thotkeeper,Isendir/thotkeeper