Add a --coverage option to 'python setup.py test' and 'python setup.py trial'. refs #1698

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
Delete useless stuff from Makefile.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
Update coverage-related targets in Makefile. refs #1698

Signed-off-by: Daira Hopwood <daira@jacaranda.org>
Update .PHONY declarations in Makefile.

Signed-off-by: Daira Hopwood <daira@jacaranda.org>