better test coverage

documentation

Way to "register" handler classes, such that the base Chunk class automatically
re-blesses itself into that class.  e.g., LIST/INFO class, RIFF/WAVE class,
IENG class, etc.  Chunk should do the read_header/data, and then call an oninit
List class should do the same for LISTs.

ability to specify chunks by their "path" (made up of "type"s of nested
containers; multiple chunks having the same "id" and "type" in the same
parent container can be differentiated by order; or, defaults to first match)
ex: "INFO/IAUT"; if multiple IAUT's, "INFO/IAUT1" -- assume 0 if not specified

ability to leave data on disk instead of slurping everything into memory

ability to do buffered read/write of data

RIFX

way to validate that the appropriate chunks for a given type are present
