Make a metadata class, based on dict, which allows output of lists as strings.

[LordSputnik]

Traceback (most recent call last):
  File "warp.py", line 267, in <module>
    fetched_release = FetchNextRelease()
  File "warp.py", line 80, in FetchNextRelease
    result.Fetch()
  File "~/mb-masstagger/Warp/release.py", line 59, in Fetch
    self.__ProcessData()
  File "~/mb-masstagger/Warp/release.py", line 116, in __ProcessData
    run_album_metadata_processors(None, self.processed_data, self.data)
  File "~/lordsputnik/mb-masstagger/Warp/release.py", line 166, in run_album_metadata_processors
    processor(tagger, metadata, release)
  File "./Warp/plugins/wavedash.py", line 28, in fix_album_wavedash
    metadata[field] = re.sub(old, new, metadata[field])
  File "/usr/lib/python2.7/re.py", line 151, in sub
    return _compile(pattern, flags).sub(repl, string, count)
TypeError: expected string or buffer