issues

- remaining error todos
    - Make sure that user's can't do thing like add <hi> tags 
      in invalid locations.
- document everything
- allow for some filter to ignore certain properties
- refactor addContent() of Subflow, HighlightTag, and TUV
    - I might need to break out these into more type-specific 
      adders
- need a way to report errors when writing
    - eg what if we try to write a tu that doesn't include a tuv of the
      source locale.  is this a warning?  error?
- util code to serialize TUV data to something legible would be nice
- use xmlunit
- arguably TUVBuilder should only support build() at the top level, 
  nested builders shouldn't
    - this becomes tricky to implement because of the method chaining.
      if build() is in a subclass, the return value will be something
      that would need to be cast down in order to call it.
- writer needs to throw errors if you call things at the wrong time
- what is the correct behavior of calling TUVBuilder.build() multiple times
- support <map> and <ude>
- throw an exception if no source language TUV is present when a TU is
  written?  This is actually stricter than the spec demands.  I 
  may need a strict mode.
- unittest to show i'm ignoring case when comparing TUV locales
- unittest to show i'm writing src locale first
- BaseTUVContentSink.addContents() should use a bounding wildcard
- I think there may be cases related to case-insensitive languages 
  that I'm not handling correctly.
- There's nothing in the spec that prevents a single TU from having
  multiple TUVs with the same language.  What is the best behavior?
- might be nice to provide some basic tools (rewrite locale, maybe some 
  sort of sed/awk-type thing for editing TUs).  Should I bundle this,
  or make it a separate project?
- refactor segmentbuilder validation logic with stuff called from tuvbuilder
- handle duplicate properties on a tu

- repackage
- test woodstox - is it faster?