educe.stac.graph.recursive_cdu_heads()

Recursively digs up the 'head' EDU for any given CDU
educe.stac.graph.without_cdus()

Deep copy of the graph and underlying annotations but without the
CDUs. Anything pointing from/to a CDU instead uses the deep head.
API doc for educe.stac.tests (grumble)

We don't really want this but I haven't figured out a good
way to separate the test hierarchy that would allow us to
reflect the package hierarchy, and be automatically detected
by nose