ignore_missing=False does not work with OrderedDict

[kpsherva]

In general for testing model.do(blob, ignore_missing=False) (f.e test_videos_video.py:33) should work to catch all fields which were missed in the analysis, and have no implemented rules, to avoid loosing data during cleaning or migration.
How to recreate:

1. put in tests a field with no matching rule.
2. call in tests method model.do with ignore_missing=False.
3. GroupableOrderedDict will create key __ordered__ for the parsed XML and it will be recognised as a MARC field name later, which has no rule -> ignore_missing will raise and exception for that "missing" rule.

Temporarily solved with setting ordered=False in the GroupableOrderedDict -> (#155)
@egabancho mentioned of having similar issue in the past.