Use DjangoJSONEncoder - which handles additional django types

[mzdeb]

All supported types: https://docs.djangoproject.com/en/1.11/topics/serialization/#djangojsonencoder

Without this change serialization of:

class Job(models.Model):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4)

throws exception:

[...]
File "/home/vagrant/env/lib/python3.4/site-packages/ajax_select/fields.py", line 444, in make_plugin_options
    'plugin_options': mark_safe(json.dumps(po)),
  File "/usr/lib/python3.4/json/__init__.py", line 230, in dumps
    return _default_encoder.encode(obj)
  File "/usr/lib/python3.4/json/encoder.py", line 192, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/usr/lib/python3.4/json/encoder.py", line 250, in iterencode
    return _iterencode(o, 0)
  File "/usr/lib/python3.4/json/encoder.py", line 173, in default
    raise TypeError(repr(o) + " is not JSON serializable")
TypeError: UUID('998109d4-cf99-42d5-af34-c6b7ba16423a') is not JSON serializable

[crucialfelix]

Thanks. Looks useful.

[mzdeb]

My pleasure! :)