Add a test_runner option

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Issue #148 new
Damien Lebrun created an issue

I tried to convert my tests to unittest2 (I need the skip decorators) and it worked when run by unittest2 but not really with setup test command; it's raised a warning (unittest2/ DeprecationWarning: Use of a TestResult without an addSkip method is deprecated self._addSkip(result, skip_why) and test shows as OK instead of SKIPED.

Would it be possible to set a test runner other unittest.main?