No module named 'jsonschema.compat'

[davimenezesoli]

Describe the bug
We are getting the error saying that the module is named jsonschema.compat couldn't be found. This is happening because this file was removed from the jsonschema package. See: python-jsonschema/jsonschema#843

Example Schema and code

Traceback (most recent call last):
  File "./client.py", line 6, in <module>
    import python_jsonschema_objects as pjs
  File "/usr/local/lib/python3.6/dist-packages/python_jsonschema_objects/__init__.py", line 12, in <module>
    from jsonschema.compat import iteritems
ModuleNotFoundError: No module named 'jsonschema.compat'

Expected behavior
The error should not happen. Looks like the other package is changing the method to use .items() instead of iteritems(). Maybe the same thing can be updated here.

[cwacek]

Fixed in #224