Fixes issue 331
previously to this change the collection code would issue a warning for
when ever it encountered a variable that looked like a test but wasn't a
function saying that it wouldn't collect it because it wasn't a function.
This fixes the logic so that if that warning is issued it really isn't
collected.
However previously special cases existed to support tests that were
created using functools.wraps and functools.partial. So the condition for
issuing that warning has been updated to take that in to account
Also try the old way of detecting functions just for proper integration
with mock.path in python 2.7 the get_real_func returned the unbound method
a3bda59a30