Changed to show used command to execute tests

[alissonperez]

First line now will show the command used to run the tests.

With this changes, output will be something like this:

Command: "~/.virtualenvs/my-env/bin/python manage.py test my.package.myTestCase.test_something"
.
----------------------------------------------------------------------
Ran 1 test in 0.247s

OK

Please, take a look and tell me what do you think.

Thanks