- Add doctest support
- Add optional code coverage support, using Ned Batchelder's coverage.py;
activate with --coverage switch or NOSE_COVERAGE environment variable
- More informative error message on import error
- Fix bug where module setup could be called twice and teardown skipped
for certain setup method names.
- main() returns success value, does not exit. run_exit() added to support
old behavior; nosetests script now calls nose.run_exit()