tags() methods have inconsistent argument order

[Jonathan Lange]

$ bzr ls -VR --kind=file --null | xargs -0 grep -In def\ tags
python/subunit/__init__.py:168:def tags_to_new_gone(tags):
python/subunit/__init__.py:1107: def tags(self, new_tags, gone_tags):
python/subunit/test_results.py:86: def tags(self, gone_tags, new_tags):
python/subunit/test_results.py:314: def tags(self, new_tags, gone_tags):

Note that python/subunit/test_results.py:86 has the reverse order to the others, and has the implementation:
    def tags(self, gone_tags, new_tags):
        return self.decorated.time(gone_tags, new_tags)

Which smells wrong, and like a gap in testing.

[Robert Collins (lifeless)]

Its pretty hard to test, as the two parameters are passed down consistently; it is however a bug and I'm just going to land the obvious fix in trunk.