Add ``dates`` and ``acknowledgements`` fields to ``Challenge``.
Fix Snippet failing test, ``image`` field is blank.
Update ``Events`` model description.

https://github.com/madewithbytes/us_ignite/issues/166

The models have been updated to match expected
fields.
Add admin inline forms for the ``EventURLs``.

https://github.com/madewithbytes/us_ignite/issues/166

This will show at glance the URLs for the Events.
Update the public ``Event` form to match the new model.

https://github.com/madewithbytes/us_ignite/issues/166

The updated form allows the ``EventURLs`` in an FormSet.
Add test helper to create inline forms payload.

Usage:

    from us_ignite.common.tests import utils
    payload = utils.get_inline_payload(FormSetClass)

Where the ``FormSetClass`` is an inline formset form. Optional
keyword attributes are available:

- ``instance`` instance for the payload.
- ``data_list`` data to be bundled on every inline form.
- ``max_num`` max number of forms.

 Any extra ``kwargs`` will be added to the form payload.
Add inline formset form to the event form.

https://github.com/madewithbytes/us_ignite/issues/166

The inline form lists the optional extra links for
the ``Event``.
Load ``Snippets`` fixtures when the dummy data is added.
Load initial ``Snippets`` fixtures on the ``load_fixtures`` command.
Bugfix: Make sure ``Events`` are editable for owners.

When the ``Event`` was in ``DRAFT`` mode it wouldn't be
editable for the ``owner``.