* Had to modify tests to remove ID fields since scan order is somewhat random.
* Added test_unchanged_root() to test_scan.py. Resolves issue #83.
* Added test_changed_root() to test_scan.py, which resolves issue #84.
* Problem with test_changed_root() - wasn't actually changing the contents. Works now.
* Added test_existing_subtree() to test_scan.py. Resolves issue #86.
* Modified build_tree() in brd_unit_base.py to not remove the root directory if it already exists, and to only make the root directory if it doesn't already exist.
* Started on test_multiple_roots() in test_scan.py. Not quite working - appears to be an issue with schema 3's fingerprints.
* Changed test_multiple_roots() to use another schema 1. Closes issue #85.