py-nose2: updated to 0.7.4

0.7.4:
Fixed
* Respect fail_under in converage config
* Avoid infinite recursion when loading setuptools from zipped egg
* Manpage now renders reproducably
* MP doc build now reproducable

Features
*  Setup tools invocation now handles coverage

Notes
* Running nose2 via setuptools will now trigger CreateTestsEvent and CreatedTestSuiteEvent

(adam)